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PART I DEACTIVATION OF TRIPLET PHENYL ALKYL KETONES BY CONJUGATIVELY ELECTRON-HITHDRAWING SUBSTITUENTS PART II REGIOELECTRONIC CONTROL OF INTRAMOLECULAR CHARGE-TRANSFER QUENCHING IN VARIOUS EXCITED TRIPLET PHENYL KETONES By Elizabeth Jane Siebert A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Chemistry 1981 ABSTRACT PART I DEACTIVATION OF TRIPLET PHENYL ALKYL KETONES BY CONJUGATIVELY ELECTRON-NITHDRAHING SUBSTITUENTS PART II REGIOELECTRONIC CONTROL OF INTRAMOLECULAR CHARGE-TRANSFER QUENCHING IN VARIOUS EXCITED TRIPLET PHENYL KETONES By Elizabeth Jane Siebert PART I Substituent effects on both photoreactivity (y-hydrogen abstrac- tion) and triplet energies (n,n* and n,n*) of phenyl alkyl ketones were' determined for conjugatively electron-withdrawing substituents (cyano, carbomethoxy, and acyl). Spectroscopic results indicate that para {-R) substituents stabilize the n,n* triplet much more than the n,n* triplet, resulting in n,n* lowest triplets. Conversely, meta (-R) substituents do not stabilize n.n* triplets sufficiently to invert the triplet levels. Ortho (-R) substituents are dominated by steric factors: o-cyano stabilizes the n,n* triplet, whereas o-carbomethoxy stabilizes the n,n* triplet. These results support a largely Elizabeth Jane Siebert l,4-biradical structure for the n,n* triplet and suggest resonance stabilization by the para (-R) substituents. Since only the n,n* triplet is reactive toward hydrogen abstrac- tion, substituent effects on triplet energies can also be determined from triplet photoreactivities. In agreement with the spectroscopic results, para (-R) substituents and ortho-carbomethoxy (n,n* lowest triplets) decrease triplet reactivity, while meta (-R) substituents and ortho-cyano (n,n* lowest triplets) increase reactivity in both benzene and acetonitrile. All (-R) substituted ketones undergo charge transfer quenching at nearly diffusion controlled rates. Various correlations involving Hammett parameters, reduction potentials, and n,n* triplet energies for various substituted valerophenones are presented. PART II Intramolecular charge transfer (CT) quenching rates were determined for amino-ketones in which the amine moiety was permitted only limited access to the site of triplet excitation. Rapid internal quenching 8 s") was found in para-valeryl B-dimethylaminoethyl “(mm 5 x IO benzoate (p-ZVB), which has a n.n* lowest triplet. The conformation- ally similar para-benzoyl B-dimethylaminoethyl benzoate, p-ZBB, (n,n* lowest triplet) displayed slower internal quenching (kCT «.105 5") as determined from its phosphorescence lifetime and quantum yield. Para-valeryl y-dimethylaminopropyl benzoate (n,n* lowest triplet) also undergoes rapid CT quenching whereas both m-ZVB and m-ZBB (n,n* lowest triplets) undergo little internal quenching. Since the amine Elizabeth Jane Siebert moiety cannot possibly come into contact with the carbonyl in any of these molecules, the results suggest that excitation in n,n* triplets is centered on the phenyl ring and excitation in n,n* triplets is localized on the carbonyl. Rapid CT quenching was observed for p-methoxy-y-dimethylamino- butyrophenone in both benzene and acetonitrile (kCT «.108 - 109 s"), while significant internal CT quenching (ch «:107 5") was observed for p-(3-dimethylaminapropoxy)valerophenone only in acetonitrile. These results suggest charge separation in the n,n* triplet, stabilized by polar solvents. To Mom and Dad and Barney ii ACKNOWLEDGMENTS The author wishes to thank Professor Peter J. Wagner for his guidance and support throughout the course of this endeavor. His advice to emulate his chemistry and not his desk hopefully will be heeded in the future. Also, the memos "signed" by Peter J. Wagner will always be remembered. The author would like to thank the members of the Wagner Group for all the memorable times shared at MSU. Special thanks to (M. A. Meador‘)2 for all the late night discussions, to the Kondili for their lasting friendship, and to R. Young for all the nickels. ' Also, hearty thanks to F. D. for the new beginning. The author would also like to thank both relatives and friends for their encouragement and Mrs. Peri-Anne Narstler for the excellent typing of this dissertation. Finally, the author would like to thank the Chemistry Department at MSU for the financial support and use of its facilitites and the National Science Foundation for the research assistantships ad- ministered by Dr. Wagner. TABLE OF CONTENTS Chapter Page LIST OF TABLES ....................... viii LIST OF FIGURES ...................... xviii INTRODUCTION ........................ l A. Photophysical Processes .............. l B Norrish Type II Photochemical Reaction ....... 3 C. Triplet States of Phenyl Alkyl Ketones ....... 4 D Energy Transfer and Charge Transfer Processes ..................... 9 1. Energy Transfer ................ 9 2. Charge Transfer Processes ........... l2 E. Stern-Volmer Kinetics ............... 25 F. Research Objectives ................ 26 l. Part I: Deactivation of Triplet Phenyl Alkyl Ketones by Conjugatively Electron-Withdrawing Substituents ....... 26 2. Part II. Regioelectronic Control of Intramolecular Charge-Transfer Quench- ing in Various Excited Triplet Phenyl Ketones ......................................... 27 PART I - DEACTIVATION OF TRIPLET PHENYL ALKYL KETONES BY CONJUGATIVELY ELECTRON- NITHDRAHING SUBSTITUENTS .............. 30 RESULTS ........................... 31 A. Photokinetic Studies ................ 3l l. Stern-Volmer Quenching Studies ......... 31 iv Chapter 2. Quantum Yields ................. 3. Maximum Quantum Yields ............. 4. Disappearance Quantum Yields .......... 5. Intersystem Crossing Yields .......... 6. Photoreduction Experiments ........... B. Spectroscopy .................... l. Phosphorescence Emission Spectra ........ DISCUSSION ......................... A. Models for Substituent Effects on Triplet Energies .................. B. Triplet Energies of Substituted Valerophenones ................... C. Electronic Absorption Spectra and Cyclic Voltammetry . . . .- ............. D. Rationalization of Substituent Effects on Both n,n* and n,n* Triplet States ........ E. Type II Quantum Yields ............... F. Determination of kd Values by Various Methods ....................... G. Ketone Photoreactivity and Calculation of Relative Triplet Energies ............ H. Attempted Correlation of Reactivities with Hammett a Values ................ 1. Charge Transfer Quenching Studies .......... J. .Correlation of Reduction Potentials with Hammett a Values .................. K. Correlation of n,n* Triplet Energies for Substituted Phenyl Ketones with Hammett a Values ...................... L. Correlation of n,n* Triplet Energies with Reduction Potentials ................ Page 40 4O 50 50 51 51 51 69 69 7O 73 75 BI 82 84 86 88 94 97 Chapter Page ”PART II - REGIOELECTRONIC CONTROL OF INTRA- MOLECULAR CHARGE TRANSFER QUENCHING IN VARIOUS PHENYL KETONES ............. 102 RESULTS .......................... 103 l. Stern-Volmer Quenching Studies .......... 103 2. Quantum Yields .................. 113 3. Disappearance Quantum Yields ........... 113 DISCUSSION ........................ 120 A. Bifunctional Molecules .............. 120 B Amino-Esters ................... 121 C. Amino-Ethers ................... 128 D Summary of Charge Transfer Quenching Results ...................... 131 E. Suggestions for Further Research ......... 135 EXPERIMENTAL ....................... 138 A. Preparation and Purification of Chemicals ..................... 138 l. Solvents and Additives ............ 138 2. Internal Standards .............. 141 3. Quenchers ................... 142 4. Ketones .................... 144 B. Photokinetic Techniques .............. 161 1. General Procedure ............... 161 2. Stern-Volmer Quenching Studies and Quantum Yields ................ 165 3. Disappearance Yields ............. 166 4. Intersystem Crossing Yields .......... 167 5. Photoreduction ................ 168 C. Spectra ...................... 168 vi Chapter Page 1. Phosphorescence Emission Spectra ....... 168 2. Electronic Absorption Spectra ......... 169 3. Infrared Spectra ............... 169 4. 1H NMR Spectra ................ 169 5. Mass Spectra ................. 170 6. Cyclic Voltammetry .............. 170 APPENDIX ......................... 172 REFERENCES ........................ 262 vii Table LIST OF TABLES Photokinetic Parameters for Ring- Substituted Valerophenones .......... Photokinetic Parameters for Phenyl Alkyl Ketones as a Function of y-Substi- tution .................... Spectroscopic Data fer Ring-Substituted Valerophenones ................ Spectrosopic Data fer Other Ring-Sub- stituted Valerophenones ........... Substituent Effects on Triplet Energies of Model Compounds .............. UV Spectroscopic Data ............ Predicted n,n* - n,n* Separations in Substituted Valerophenones in Benzene at Room Temperature ............. Relative Substituent Effects on Reduc- tion Potentials of Substituted Valero- phenones ................... Charge Transfer Quenching Data for Substituted Valerophenones .......... viii Page 32 34 56 57 59 64 71 76 90 Table 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Page Charge Transfer Quenching Parameters in Benzene ................... 92 Correlation of Hammett 0 Values with Reduction Potentials for Valerophenones ..... 95 Photokinetic Data for Valerophenone Models ..................... 107 Photokinetic Data for Amino-Esters ....... 108 Photokinetic Data for Amino-Ethers ....... 109 Phosphorescence Data for Substituted Benzophenones .................. 114 Charge Transfer Quenching Data for Valerophenone Models .............. 125 Charge Transfer Quenching Data for Amino-Esters .................. 127 Charge Transfer Quenching Data for Amino-Ethers .................. 130 Summary of Charge Transfer Quenching Results ..................... 132 Quenching of 0.039 M Valerophenone by Hexadiene in Benzene .............. 173 Quenching of Valerophenone by Hexa- diene in Acetonitrile .............. 174 Quenching of Valerophenone by Tri- ethylamine in Benzene .............. 175 . Quenching of Valerophenone by Tri- ethylamine in Acetonitrile ........... 176 ix Table 24 25 26 27 28 29 3O 31 32 33 34 35 Quenching of 0.040 M Butyrophenone by Hexadiene in Benzene ............. Quenching of o-Cyanovalerophenone by Hexa- diene in Benzene ............... Quenching of 0.040 M o-Cyanovalerophenone by Pentadiene in Acetonitrile ......... Quenching of m-Cyanovalerophenone by Hexa- diene in Benzene ............... Quenching of 0.039 M m-Cyanovalero- phenone by Hexadiene in Acetonitrile ..... Quenching of m-Cyanovalerophenone by Tri- ethylamine in Benzene ............. Quenching of m-Cyanovalerophenone by Tri- ethylamine-n1Acetonitrile ........... Quenching of p-Cyanovalerophenone by Hexadiene in Benzene ............. Quenching of 0.040 M p-Cyanovalerophenone by Hexadiene in Acetonitrile ......... Quenching of p-Cyanovalerophenone by Tri- ethylamine in Benzene ............. Quenching of 0.042 M p-Cyanovalerophenone by Low Concentrations of Triethylamine in Benzene .................. Quenching of 0.037 M p-Cyanovalerophenone by Triethylamine in Acetonitrile ....... Page 177 178 179 180 181 182 183 184 185 186 188 189 Table 36 37 38 39 4O 41 42 43 44 45 46 47 Quenching of 0.041 M p-Cyanobutyro- phenone by Hexadiene in Benzene ........ Quenching of 0.040 M p-Cyanobutyro- phenone by Hexadiene in Benzene ........ Quenching of 0.037 M p-Cyano- yMethyl- valerophenone by Hexadiene in Benzene ..... Quenching of o-Carbomethoxyvalerophenone by Hexadiene in Benzene ............ Quenching of 0.041 M o-Carbomethoxyvalero-» phenone by Hexadiene in Acetonitrile ..... Quenching of o-Carbomethoxyvalerophenone by Triethylamine in Benzene .......... Quenching of o-Carbomethoxyvalerophenone by Triethylamine in Acetonitrile ....... Quenching of m-Carbomethoxyvalerophenone by Hexadiene in Benzene ............ Quenching of m-Carbomethoxyvalerophenone by Pentadiene in Acetonitrile ......... Quenching of 0.040 M m-Carbomethoxyvalero- phenone by Triethylamine in Benzene ...... Quenching of p-Carbomethoxyvalerophenone by Hexadiene in Benzene ............ Quenching of p-Carbomethoxyvalerophenone by Hexadiene in Acetonitrile ......... xi Page 190 191 192 193 195 196 197 198 199 200 201 202 Table 48 49 50 51 52 53 54 55 56 57 58 59 Quenthing of p-Carbomethoxyvalerophenone by Triethylamine in Benzene .......... Quenching of p-Carbomethoxyvalerophenone by Triethylamine in Acetonitrile ........ Quenching of m-Divalerylbenzene by Hexa- diene in Benzene ................ Quenching of 0.032 M m-Divalerylbenzene by Hexadiene in Acetonitrile .......... Quenching of 0.029 M m-Divalerylbenzene by Triethylamine in Benzene ............ Quenching of m-Divalerylbenzene by Tri- ethylamine in Acetonitrile ........... Quenching of p-Divalerylbenzene by Hexa- diene in Benzene ................ Quenching of p-Acetylvalerophenone by Hexadiene in Benzene .............. Quantum Yields for 0.040 M Trifluoro- methylvalerophenones in Benzene ........ Disappearance Quantum Yields for Cyano- valerophenones in Benzene ........... Disappearance Quantum Yields for Cyano- valerophenones in Benzene ........... ‘Disappearance Quantum Yields for Cyano- valerophenones in Acetonitrile ......... xii Page 203 204 206 207 208 209 210 211 212 213 214 215 Table 60 61 62 63 64 65 66 67 68 69 70 Disappearance Quantum Yields for Carbo- methoxyvalerophenones in Acetonitrile ...... Disappearance Quantum Yields for Carbo- methoxyvalerophenones in Acetonitrile ...... Maximization of ¢II for 0.040 M p—Cyano- valerophenone by Pyridine in Benzene ...... Maximization of °II for 0.041 M p-Cayno- valerophenone by Dioxane in Benzene ....... Maximization of III for 0.040 M p-Cyano- valerophenone by t-Butyl Alcohol in Benzene ..................... Maximization of III for 0.040 M p-Cyano- butyrophenone by Pyridine in Benzene ...... Effect of Ketone Concentration on ¢II for p-Carbomethoxyvalerophenone in Acetonitrile .................. Intersystem Crossing Yield for 0.040 M p-Cyanoacetophenone in Benzene ......... Intersystem Crossing Yield for 0.050 M p- Carbomethoxyvalerophenone in Benzene ...... Quenching of 0.050 M p-Cyanoacetophenone by Naphthalene in Acetonitrile (1.0 M Toluene) .................... Photoreduction of 0.051 M p-Cyanoaceto- phenone by Toluene in Acetonitrile ....... xiii Page 216 217 218 219 220 221 222 223 224 225 226 Table 71 72 73 74 75 76 77 78 79 Page Quenching of 0.050 M p-Cyanoacetophenone by Naphthalene in Dry Acetonitrile (1.0 M p-Xylene). .' .............. 227 Photoreduction of 0.050 M p-Cyanoaceto- phenone by p-Xylene in Dry Acetonitrile . . . . 228 Quenching of 0.040 M p-Carbomethoxyvalero- phenone by B-Dimethylaminoethyl Benzoate in Benzene ................... 229 Quenching of p-Carbomethoxyvalerophenone by B-Dimethylaminoethyl Benzoate in Aceto- nitrile .................... 230 Quenching of 0.040 M p-Carbomethoxyvalero- phenone by y-Dimethylaminopropyl Benzoate in Benzene ................... 231 Quenching of 0.040 M p-Carbomethoxyvalero- phenone by v-Dimethylaminopropyl Ben- zoate in Acetonitrile ............. 232 Quenching of 0.040 M m-Carbomethoxyvalero- phenone by B-Dimethylaminoethyl Benzoate in Acetonitrile ................ 233 Quenching of p-Methoxyvalerophenone by Pentadiene in Benzene ............. 234 Quenching of p-Methoxyvalerophenone by Pentadiene in Acetonitrile ........... 235 xiv Table 81 82 83 84 85 86 87 88 89 90 91 Quenching of 0.040 M p-Methoxyvalerophenone by N,N-Dimethy1aminopropy1 Phenyl Ether in Acetonitrile ................ Quenching of 0.020 M p-2VB by Pentadiene in Benzene ................... Quenching of 0.030 M p-2VB by Pentadiene in Benzene ................... Quenching of 0.040 M p-ZVB by Pentadiene in Benzene ................... Quenching of 0.010 M p-ZVB with Pentadiene in Acetonitrile . . °- ............. Quenching of 0.020 M p-ZVB by Pentadiene in Acetonitrile ................ Quenching of 0.040 M p-2VB by Pentadiene in Acetonitrile .................. Quenching of 0.060 M p-2VB of Pentadiene in Acetonitrile ................ Quenching of 0.080 M p-2VB of Pentadiene in Acetonitrile ................. Quenching of 0.10 M p—2VB by Pentadiene in Acetonitrile ................ Quenching of 0.020 M p-3VB by Pentadiene in Acetonitrile ............... Quenching of 0.040 M p-3VB by Pentadiene in Acetonitrile ............... XV Page 236 237 238 239 240 241 242 243 244 245 246 247 Table 92 93 94 95 96 97 98 99 100 '101 102 103 Quenching of 0.060 M p-3VB by Pentadiene in Acetonitrile ................ Quenching of 0.10 M p-3VB by Pentadiene in ACetonitrile ................ Quenching of 0.020 M m-2VB by Pentadiene in Benzene ................... Quenching of m-2VB by Pentadiene in Acetonitrile .................. Effect of Ketone Concentration on II for p-2VB and p-3VB in Acetonitrile ...... Disappearance Quantum Yields for p-ZVB and p-ZAB in Acetonitrile ........... Quenching of 0.020 M p-Me03E by Penta- diene in Acetonitrile ............. Quenching of p-3VE by Pentadiene in Benzene .................... Quenching of Ketone Disappearance for p- 3VE and p-2AE by Pentadiene in Acetonitrile . . Phosphorescence Lifetime for 1.0 x 10'4 M m-Carbomethoxybenzophenone and Irel 4 for 1.0 x 10- M m-ZBB in CCl4 ......... Phosphorescence Lifetime for 1.0 x 10"4 M p-Carbomethoxybenzophenone and Irel for 4 1.0 x 10' M p-ZBB in CCl 4 00000000000 Phosphorescence Lifetime for 1.0 x 10'4 M p-ZBB in CC14 ................ xvi Page 248 249 250 251 252 253 255 256 257 258 259 260 Table Page 104 Quenching of 0.040 M Butyrophenone in CCl4 ...................... 261 xvii Figure LIST OF FIGURES Modified Jablonski Diagram for Phenyl Alkyl Ketones ................ Stern Volmer Plots for Substituted Valerophenones in Benzene with Diene Quencher (O H;.o-CN;Am-CN;Ip-CN) . . . . Stern Volmer Plots for Substituted Valerophenones in Acetonitrile with Diene Quencher ( O H; O o-CN;A m-CN; II p-CN) .................. Stern Volmer Plots fer Substituted Valerophenones in Benzene with Diene Quencher (O o-CDZCH3; Um-c02ca3; A p-COZCH3) ................ Stern Volmer Plots for Substituted Valerophenones in Acetonitrile with Diene Quencher ( O o-COZCH3; E] m- cozcn3;Ap-cozcn3) ............. Stern Volmer Plots fbr Substituted Valerophenones in Benzene with Diene Quencher (An-cocH3; g p-COC4H9; O m-C0C4H9; .m-C0C4H9 in acetonitrile) . . . xviii Page 35 36 37 39 Figure Page 7 Stern Volmer Plots for Substituted Valerophenones in Benzene (0.5 M Pyri- dine) with Triethylamine Quencher ((3 H; 1:] n-cu;Ap-CN) ................ 41 8 Stern Volmer Plots for Substituted Val- erophenones in Acetonitrile with Tri- ethylamine Quencher (0 H; E] m-CN; A p-CN) ................... 42 9 Stern Volmer Plots for Substituted Val- erophenones in Benzene (0.5 M Pyridine) with Triethylamine Quencher (C) o-COZCH3; L'J m-cozcn3;A p-COZCH3) ........... 43 10 Stern Volmer Plots fOr Substituted Val- erophenones in Acetonitrile with Tri- ethylamine Quencher (C) o-COZCH3; A p-cozcu3) ................. 44 11 Stern Volmer Plots for m-Divalerylbenzene in Benzene (0.5 M Pyridine)() and Aceto- nitrileEl with Triethylamine Quencher ..... 45 12 Stern Volmer Plot for p-Cyanovalero- phenone in Benzene (0.5 M Pyridine) and Low Triethylamine Quencher Concentrations. . . 46 13 Maximization of II for p-Cyanovalerophenone in Benzene with Added t-Butyl Alcohol 0 and Added PyridineA ............... 47 xix Figure Page 14 Maximization of QII for p-Cyanovalero- phenone in Benzene with Added Dioxane ..... 48 15 Stern Volmer Plots for p-Cyanophenyl Alkyl Ketones in Benzene with Diene Quencher (E3 p-Cyanobutyrophenone; Ap-Cyanovalerophenone; O p-Cyano- - methylvalerOphenone) ............. 49 16 Results from Reaction of p—Cyanoaceto- phenone and Toluene in Acetonitrile (Formation of Bibenzyl Monitored). . ... . . . 52 17 Stern Volmer Plot for p-Cyanoacetophenone in Acetonitrile (1.0 M Toluene) with Naphthalene Quencher (Formation of Bi- benzyl Monitored) ............... 53 18 Results from Reaction of p-Cyanoaceto- phenone and p-Xylene in Acetonitrile (Formation of p-Ditolylethane Monitored) . . . 54 19 Stern Volmer Plot for p-Cyanoacetophenone in Acetonitrile (1.0 M p-Xylene) with Naphthalene Quencher (Formation of p- Ditolylethane Monitored) ........... 55 20 Phosphorescence Spectra of 10-4 M Valero- phones in 5:1 Methylcyclohexane/Iso- pentane at 77°K. Top, Valerophenone; Second, m-CyanovalerOphenone; Third, XX Figure 20 cont. 21 22 23 24 p-Cyanovalerophenone; and Bottom, 0- Cyanovalerophenone in Isopentane Glass ................... Phosphorescence Spectra of 10'4 M Valero- phenones in Isopentane at 77°K. Top, o-Carbomethoxyvalerophenone; Middle, me Carbomethoxyvalerophenone; Bottom, p- Carbomethoxyvalerophenone ......... Phosphorescence Spectra of 10'4 M Valero- phenones in Isopentane at 77°K. Top, Valerophenone (MCH/IP glass); Middle, m-Divalerylbenzene; Bottom, p-Divaleryl- benzene .................. Cyclic Voltammagrams for 10'4 M Valero- phenones in Acetonitrile (0.1 M TEAP) versus SCE (200 mV/sec). Top, Valero- phenone: Second. o-CyanovalerOphenone; Third, m~Cyanovalerophenone; Bottom, p- Cyanovalerophenone ............. 4 M Valero- Cyclic Voltammagrams for 10' phenones in Acetonitrile (0.1 M TEAP) versus SCE (200 mV/sec). Top, o-Carbo- methoxyvalerophenone; Middle, m-Carbo- methoxyvalerophenone; Bottom, p-Carbo- methoxyvalerophenone ............ xxi Page 60 61 62 65 66 Figure 25 26 27 28 29 Cyclic Voltammagrams for 10'4 Valero- phenones in Acetonitrile (0.1 M TEAP) versus SCE (200 mV/sec). pr, m-Di- valerylbenzene; Middle, p-Divaleryl- benzene; Bottom, p-Acetylvalerophenone. . . . Cyclic Voltammagrams for 10'4 M Valero- phenones in Acetonitrile (0.1 M TEAP) versus SCE (500 mV/sec). Top, o-Tri- f1uoromethylvalerophenone; Middle, p- Trifluoromethylvalerophenone; Bottom, m-Trifluoromethylvalerophenone ........ Plot of Relative kobs Values as a Function of Ground State Hammett 0 Values. 0 , -I Substituents;G, Elec- tron-donating Substituents;€9. para-R Substituents;.. p-c1;D . p-scr3 ...... Correlation of Charge Transfer Quench- ing Rates fbr Substituted Valerophenones in Benzene (0.5 M Pyridine) with Ex- cited State Reduction Potentials: O, n,:r* Lowest Triplet;El 1r,n* Lowest Triplet ................... Correlation of Half-wave Reduction Po- tentials for Substituted Valerophenones with Hamnett om and o ' Values: 0 meta- P xxii Page 67 68 87 91 Figure 29 cont. 30 31 32 33 34 Substitution; E1 para-Subs ti tuti on ...... Correlation of n,n* Triplet Energies (4:1 MCH/IP, 77°K)of Substituted Benzo- phenones with Hamett Parameters.89a U . I (-R) Substituents;., I Values Added From This Study ............ Correlation of n,n* Triplet Energies (4:1 MCH/IP, 77°K) of Substituted Benzo- phenones with Haumett Parameters: D , I (-R) Substituents;o. Cl Values Taken From Reference 89a ............. Attempted Correlation of n,n* Triplet Energies (Isopentane, 77°K) with Half- wave Reduction Potentials for Substituted Valerophenones: O n,1r* Lowest Triplets; [J'n,n* Lowest Triplets ........... Attempted Correlation of n,n* Triplet Energies (Ethanol, 77°K) with Half-wave Reduction Potentials for Substituted Valerophenones: C) n,n* Lowest Triplets; I 1r,1r* Lowest Triplets ........... Stern Volmer Plots for Diene Quenching of 0.020 M Ketones: C) p2VB in Benzene; O p2VB in Acetonitrile;A p3VB in Aceto- nitrile;1:] m2VB in Benzene; and-m2VB in Acetonitrile ................ xxiii Page 96 98 98 100 101 104 Figure Page 35 Stern Volmer Plot for Diene QuenChing of 0.020 M p3VE in Benzene ............ 105 36 Stern Volmer Plot for Diene Quenching of 0.020 M p-Me03E in Acetonitrile ...... 106 37 Extrapolation of Triplet Lifetimes of p2VB C) and p3VB.(D in Acetonitrile ...... 110 38 "Stern Volmer Plot for Diene Quenching of Room Temperature Phosphorescence of m- Carbanethoxybenzophenone O and p-Carbomethoxy- benzophenone 1| in CCl4 ............ 111 39 Stern Volmer Plot for Diene Quenching of Room Temperature Phosphorescence of p288 in CC14 ................. 112 40 Stern Volmer Plot for 0.040 M Butyrophenone in CCl4 with Hexadiene Quencher'C) or Triethylamine Quencher O .......... 115 41 Extrapolation of III for p2VBO and p3VB O in Acetonitrile to Infinite Dilution . . . 116 42 Extrapolation of ¢II for m2VB in Aceto- nitrile to Infinite Dilution ......... 117 43 Extrapolation of é-K for p2VB C) and p2AB . in Acetonitrile to Infinite Dilution ................... 118 xxiv INTRODUCTION A. Photophysical Processes Molecules can undergo a wide variety of photophysical and photo- chemical processes upon the absorption of light. In order to under- stand better the photochemical reactions that phenyl alkyl ketones undergo, the many available photophysical processes will be discussed briefly. A modified Jablonski diagram] for phenyl alkyl ketones shows the photophysical processes which can occur in the absence of photo- chemical reactions (Figure 1). In this diagram the absorption and Sn : I __J III k 51—— . '0' T‘ . Th «‘2 oil in: k} Nil kill $o- Figure 1. Modified Jablonski Diagram for Phenyl Alkyl Ketones. emission of light are depicted by straight lines whereas radiation- less transitions are shown as wavy lines. A molecule absorbs a photon and is excited to an upper singlet state which rapidly under- 012 s") to the lowest excited singlet 6 goes internal conversion (kic’b 1 5'1), radiationless 3 51.2 51 can then undergo ffiuorescence (kfvt 10 decay (kd N 107 5'1), or intersystem crossing to the triplet state. The rate of intersystem crossing depends on the amount of spin- orbit coupling which allows the singlet to attain some triplet character.4 The extent of spin-orbit coupling depends both on the energy gap between S1 and the triplet state3 and the nature of the 4a singlet and triplet states. Both experimental observations and selection rules derived from electronic overlap integrals suggest that intersystem crossing from an n,n* singlet to a n.n* triplet is approximately 103 times faster than from an n,n* singlet to an n,n* triplet.4b’c For phenyl alkyl ketones, which possess n,n* lowest singlets, the rate of intersystem crossing is extremely fast (k 'M 1010 s").5 ISC Thus, fluorescence and radiationless decay are too slow to be com- petitive singlet processes. Essentially all the singlets undergo spin inversion to populate the upper vibrational states of the triplet(s). Again, rapid internal conversion (kic’b 1012 5") leads to population of the lowest vibrational level of the triplet(s).2 In many phenyl alkyl ketones, two triplets (n,h* and n,n*) are in 5 close proximity and undergo vibronic coupling or thermal equilibra- 6 tion before undergoing reaction or decay. The triplet(s) can then undergo phosphorescence (kp m 10.1 to 103 5") or radiationless decay if other photochemical processes are unavailable.3 For many phenyl alkyl ketones, hydrogen abstraction is very fast compared to both radiationless decay and phosphorescence, and thus photochemi- cal reaction leading to product formation is the major pathway fbr deactivation of the triplet state. B. Norrish Type II Photochemical Reaction The Norrish Type II photochemical reaction is the major decay process for most phenyl alkyl ketones possessing y-hydrogens. This reaction was first discovered in 1934 by Norrish and Appleyard7 when they feund that methyl butyl ketone photodecomposes to give acetone and propene in the gas phase. Further investigation of other ketones showed a characteristic a,B-bond cleavage to give a smaller carbonyl compound and an olefin.8 In 1958 Yang and Yang9 reported the formation of cyclobutanols as minor products in addition to cleavage products and suggested the formation of a 1,4-biradica1 intermediate to explain the results. Further evidence supporting the 10 and others.11 intermediacy of a 1,4-biradical was provided by Wagner Thus. y-hydrogen abstraction by the triplet state to fbrm a 1,4-bi- radical, followed by cleavage or cyclization is the generally ac-: cepted mechanism for the Norrish Type II photochemical reaction (Scheme 1). The 1,4-biradica1 also can undergo reverse hydrogen transfer to give ground state ketone.10a The addition of a Lewis base suppresses the reversion of the biradical to starting ketone by hydrogen bonding the hydroxyl hydrogen, thus slowing down reverse hydrogen transfer 1 1 «it - 3 at X X X . k'sc W kr h, \cvc knev “all )( )( ’99>‘JF"J\I‘.} . -+ gees. tui Scheme 1. Norrish Type II Photochemical Reaction. and enabling cleavage or cyclization to occur exclusively.mb’12 The quantum yield for cyclization products averages only approxi- 13 mately 10-20% of the quantum yield for cleavage products. Also, the rate of yehydrogen abstraction is dependent on both the stability of the incipient radical center,”’15 and the reactivity of the triplet state toward hydrogen abstraction. Both the electronic nature of the triplet state and the effects of substituents determine the reactivity of phenyl alkyl ketones.1]b’]6'26 C. Triplet States of Phenyl Alkyl Ketones Phenyl alkylketones possess two triplet states which differ significantly in their electronic distribution. An n,n* triplet results from excitation of a non-bonding electron of the carbonyl to a n-antibonding orbital, thus producing electron deficiency at the oxygen atom. The n,n* triplet resembles an alkoxy radical and under- goes typical radical reactions such as hydrogen abstraction.16’17 Analogously, a n,n* triplet results from excitation of a n electron to a n-antibonding orbital, resulting in increased electron density 18.19 at the oxygen atom. Consequently, the n,n* triplet is not re- active in typical electrophilic radical reactions. Valence bond representations of the two triplet states are given below. a. I 6 3m!" I “ I : Z: 3 :1 2 ’ . 311-,1'r‘ Many examples in the literature indicate that phenyl ketones with n,n* lowest triplets are reactive towards hydrogen abstraction re- actions; whereas, ketones with n,h* lowest triplets are either un- reactive or display substantially decreased reactivities. Yang and 20 Dusenbery reported that substituted benzophenones (4-methy1 or 4-trifluoromethyl) that retain an n,n* lowest triplet are easily photoreduced by 24propanol. Conversely, 4-phenylben20phenone, which possesses a n,n* lowest triplet,2] displays a 103-fold decrease in reactivity compared to benzophenone itself.22 Similarly, the photo- reduction of 4-trifluoromethylacetophenone (n,n* lowest triplet) dis- plays a six-fold increase in the rate of hydrogen abstraction, whereas 4-methylacetophenone (n,n* lowest triplet) shows a tenfold decrease in 23’24 Likewise, the Norrish reactivity, both compared to acetophenone. Type II photochemical reactions of substituted butyrophenones and valerophenones follow a similar trend: ketones with n,n* lowest triplets undergo intramolecular y-hydrogen abstraction readily, while ketones with definite n,n* lowest triplets are essentially unreac- tive.]]b’25'29 In the past two decades the determination of substituent effects on the photochemistry of phenyl ketones has received considerable attention. The effects of ring-substituents on both the triplet energies and triplet-state photoreactivity have been investigated extensively.11b’21’23424a27:28.30 In general, the effects of ring- substituents on the energies of both triplets, thus determining the nature of the lowest triplet, overshadow their electronic effects on the individual triplet states. In benzophenone the n,n* triplet is far enough below the n,n* triplet such that most substituents do not 31 cause an inversion of the two triplet states. In unsubstituted phenyl alkyl ketones the n,n* triplet lies only approximately 2.8 30b Polar solvents kcal below the n,n* triplet in nonpolar solvents. stabilize the n,n* triplet and destabilize the n,n* triplet, since the n.n* triplet has a lower dipole moment and the n,n* triplet has a higher dipole moment than the ground state."b’30d Electron-donating substituents stabilize the n,n* triplet and destabilize the n,n*. triplet, resulting in inversion of the two triplets and decreased reactivity.28 Conversely, electron-withdrawing substituents stabilize the n,«* triplet relative to the n,n* triplet and also make the n,n* triplet more electrophilic, thus making such triplets more reactive than those of unsubstituted ketones (Scheme 2). Q . 315‘" e 3 * ‘ I ~‘~__ “3“ e :BDRW' I! \)I‘ 31w“ I ‘\ 3nar" \ ‘x 34w“ «0"DKJNKIR '-tl {f'VVfTFNDHUUNlflR Scheme 2. Substituent Effects on Triplet Energies for Phenyl Alkyl Ketones. It is generally accepted that n,n* triplets are much less re- active than n,n* triplets towards hydrogen abstraction, and ketones with n.n* lowest triplets derive their reactivity primarily from equilibrium populations of upper n,n* triplets.28’32 Wagner28 has provided evidence for photoreactivity from upper n,n* triplets for p-methoxyphenyl alkyl ketones, since their rates for hydrogen ab- . straction exactly parallel the rates for unsubstituted phenyl alkyl ketones (n,n* lowest triplets) with similar y- or d-substitution. Also, the variation of photoproduct distribution with temperature for l-benzoyl-4-p-anisqy1butane is consistent with thermal equilibration of the two nonconjugated chromophores, and reaction of the anisoyl moiety from an equilibrium population of its n,n* triplet.32b At a certain temperature, T, the equilibrium population of both triplets is dependent upon the energy separation between the two triplets. AET, and fbllows a Boltzmann distribution (Equation 1) -AE RT 52.11“, T, (1) Xn,n where X is the equilibrium fractional population of a given triplet state. At room temperature the two triplets must be in close prox- imity (AET g_3 kcal) in order for thermal equilibration to occur. If the observed rate of hydrogen abstraction reflects reactivity from both triplets, then Equation (2) describes the reaction kinetics. obs n h "H ’3 XnnrkH I ankh (2) When AET §_3 kcal, reaction occurs primarily from population of the upper n,n* triplet.28 obs _ n kr ' xn,irkr (3) If the two triplets are in close proximity then vibronic coupling can induce some n,n* character into the n,n* triplet and vice versa.5 Therefore, the wave function W of the lowest triplet is a linear combination of the two unperturbed wave functions o, with the mixing coefficients a and b dependent upon both the energy gap between the triplets and symmetry considerations.5 RT] = aW(n.n*) + bw(n,n*) (4) Thus, some reactivity possibly can occur from the vibronically induced n.n* character of the n,n* triplet.23b 0. Energy Transfer and Charge Transfer Processes 1. Energy Transfer Processes a. Intermolegglar - Energy transfer is an important photo- chemical process involving a radiationless transfer of electronic excitation from a donor molecule to a suitable acceptor molecule. Triplet-triplet energy transfer (Equation 5) is the most common type of energy transfer, since the lowest triplet state of a molecule is longer-lived than the corresponding lowest singlet state and therefore has a greater probability of transferring its electronic excitation energy to a suitable acceptor molecule.32 0*(T1) + A(So)-+ 0(50) + A*(T1) (5) Triplet energy transfer can occur when the acceptor has a lower 1O 33 triplet energy than the donor molecule. Usually, the efficiency of an acceptor or quencher is determined solely by the position of its lowest triplet level and not by its molecular structure.34 In general, triplet energy transfer in solution occurs via an electron- exchange mechanism which requires diffusion of the donor and acceptor molecules to within collisional separation as a rate-limiting step.33 Thus, in relatively viscous solvents is triplet energy transfer diffusion controlled and described by a modified Debye equation.35’36 k = k = 8RT/2000 n 1 nor1 5" (6) et dif Only in solvents of low viscosity, the exothermic transfer of triplet excitation energy is not completely efficient, and an excited donor and an acceptor molecule can diffuse apart before energy transfer can occur.33’37 Since every collision between donor and acceptor does not result in energy transfer, then a conformational requirement for effective orbital overlap may be necessary in order for energy trans- 38 Wagner and coworkers39 have indicated that efficient fer to occur. energy transfer occurs at van der Waals separation (approximately 4 A for n-system overlap with a carbonyl moiety) between donor and acceptor molecules. In order to gain more insight into the conforma- tional requirements involved in energy transfer, several researchers have studied intramolecular energy transfer in systems containing isolated chromophores having known spatial dispositions relative to each other.40'43 11 b. Intrgmolecglar - There are many examples of intramolecular triplet-triplet energy transfer reported in the literature. Hammond gt_gl,4o found that triplet energy transfer from a benzophenone chromophore to a naphthalene moiety separated by one to three methylene units (the distance between the carbonyl carbon and the center of the naphthalene group is at most 10 A in all three cases) occurs with 100% efficiency with a rate constant greater than 1010 5']. Likewise. Cowan and Baum41 investigated a series of compounds in which aceto- phenone and trans-B-styryl chromophores were separated by one to four methylene units and found efficient isomerization of the styryl group upon irradiation of the benzoyl chromophore. However, the reported 20-fold decrease in the rate of triplet energy transfer in going from two to four methylene groups (ket = 7.2 x 1010 s'1 for n = 2 and ket = 3.3 x 109 s'1 for n = 4) suggests that an increase in the number of methylene units results in a decrease in the number of desirable con- fbrmations (donor and acceptor in close proximity) relative to the number of available conformations. Thus, it appears that the two chromophores have to be in close contact in order for energy transfer to occur. Also, there are a few examples of intramolecular triplet-triplet energy transfer occurring in compounds containing two isolated chromo- phores held at fixed distances in rigid molecules. Zimmerman and 42 investigated the phosphorescence emission of 1-benzoyl-4- McKelvey «z-naphthyl)-bicyclo[2.2.2]octane, in which the benzoyl chromophore (donor) and naphthyl moiety (acceptor) are separated by approximately 7 A, and found that intramolecular triplet energy transfer occurs’ 12 with 100% efficiency. In contrast, Keller and Dolby43 found that the rate constant for triplet energy transfer from benzophenone to a naphthalene group held approximately 14 A apart by a rigid steroid bridge was only 25 5'1. 43 0f even greater interest is the fact that these authors also discovered that energy transfer from a carbazole donor (n,n* lowest triplet) to a naphthalene acceptor held at a com- parable separation (approximately 15 A) was 103 times slower (ket = 0.04 5"). Thus, the conclusion was reached that triplet-triplet energy transfer is not only distance dependent but also may be struc- ture dependent, with n,n* +-n,h* triplet-triplet energy transfer being slower by three orders of magnitude than n,n* +-n,n* triplet- triplet energy transfer for the same donor-acceptor separation. 2. Charge Transfer Processes a. Intermolecular - Carbonyl compounds can be photoreduced 44 45 alkanes, 49 by a wide variety of hydrogen sources including alcohols, 45’46 47 48 and amines. alkyl benzenes, tributylstannane, ethers, It is well established that hydrogen abstraction from alcohols and alkanes by triplet carbonyls involves the simultaneous cleavage of the R-H bond and the formation of the 0-H bond to give two radical species.50 3ch = 0* + R'-H + RzC-OH + R'. .However, there are many differences in the photoreduction of ketones 13 by amines as compared to alcohols, alkanes, and many other hydrogen donors. For example, the rate of hydrogen abstraction for triplet benzophenone with alkanes depends upon the hydrocarbon C-H bond strength,51 whereas the photoreduction of benzophenone by N-alkylated diphenylamines displays little dependence on donor bond strength.52 53 reported that the photoreduction of benzophenone by Cohen and Litt triethylamine is 103 times faster than with isopropanol as hydrogen donor. Also, Cohen and Green54 found that the rate of photoreduction of acetophenone with a-methylbenzylamine was twenty times greater than the rate of photoreduction with a-methylbenzyl alcohol. Both fluor- enone and p-aminobenzophenone (n,n* lowest triplets) are not reduced by alcohols, but are readily photoreduced by tertiary amines.55’56 In order to account for the greater reactivity of amines, Cohen and 56 proposed the following mechanism involving the initial trans- Cohen fer of an electron from the nitrogen atom to the excited carbonyl. followed by proton transfer and electron redistribution. 3R c=o* + R' NCH R" :ch [R to R' 'N+CH W 2 2 2 2 2k 2 + 4 RZCOH + R'ZNCHR" The charge transfer complex can also undergo spin and charge destruc- 57 tion to give ground state ketone. Thus, charge transfer interaction between the excited carbonyl moiety and the amine can result in + k ° ' I ° u q .. l u [RZC-O R ZNCHZR ] -> RZC-O + R ZNCHZR 14 either radical fermation or deactivation to ground state ketone, depending on the nature of both the donor and acceptor molecules in- volved in the charge transfer complex.58 Rates of charge transfer interaction between donor and electron- ically excited acceptor have been fbund to be dependent on their thermodynamic properties. In 1968 Weller59 related the rate of fluores- cence quenching of aromatic hydrocarbons by amines to the change in free energy involved in electron transfer, AGCT’ which was found to be dependent on the oxidation potential of the donor, the reduction potential of the acceptor, the singlet excitation energy of the ac- ceptor, and a Coulombic term related to the free energy gained by bringing the ions to the encounter distance (Equation 7). AGCT . sin/0*) - E(A‘/A) - A‘E(A) - efi/ea (7) Weller6o determined that in solvents with large dielectric constants, the rate of charge transfer quenching of singlets produces free radical ions, and is diffusion controlled when AGCT < -10 kcal/mole. The rate constant of charge transfer quenching decreases with increas- ing AGCT and becomes proportional to exp (-AGCT/RT) when AGCT > 5 kcal/mole. Thus, when AGCT is endothermic, a plot of log kCT versus . AGcT has a slope of -16.5 eV for processes involving full electron transfer. Mataga gt_gl,6] observed the fluorescence from pyrene and N,N-dimethylaniline in various solvents. From the fluorescence quantum yields and lifetimes they concluded that in polar solvents the emiSsion was due to a strong charge transfer complex, while the 15 emission in nonpolar solvents was due to a weak CT complex (only partial electron transfer). Davis and coworkers62 showed that the rate of fluorescence quenching of fluorenone by various amines was inversely proportional to the ionization potential of the amine. Thus, Heller's equation appeared to be applicable to a large number of systems. A similar relationship was sought for the reaction of excited- 63 reported that for the state triplets with amines. Cohen and Stein photoreduction of sodium 4-benzoylbenzoate by tertiary aliphatic amines, the rate of interaction between ketone triplets and amines increased as the ionization potential of the amine decreased. In 64 related the rate constant for donor- 1972 Guttenplan and Cohen acceptor charge transfer interaction, kCT’ to the change in free energy, AGCT, fer carbonyl excited triplet states and various donors. A modified "Heller's Equation" was proposed which related AGCT to the ionization potential of the donor, the reduction potential of the acceptor, and a constant (Equation 8). 3 Eo,o + The use of the more readily available ionization potentials instead of the oxidation potentials of the donors only changes the value of the constant term. Thus, for a series of donors with a constant acceptor, log kCT «'IPD + C' and for a series of acceptors with a constant donor, log kCT m -E(A'/A) - A3Eo,o + C“. Guttenplan and Cohen64b proposed a linear correlation between log kCT and the excited 16 state reduction potential (-E(A'/A) - A3Eo o) for the quenching by triethylamine of various carbonyl acceptors, which possessed widely differing reduction potentials, triplet energies, and triplet con- 643 also reported a linear inverse rela- figurations. These authors tionship between log kCT and the donor ionization potential for the charge transfer quenching of benzophenone by various donors includ- ing amines, sulfides, mercaptans, ethers, alcohols, aromatic hydro- carbons, and olefins. TWo lines were obtained, one for aliphatic donors (slope = -0.067 mole/kcal) and the other for aromatic donors (slope 8 -0.105 mole/kcal), on a graph of log kCT versus IPD. The values of the slopes are much smaller than that observed in systems involving full electron transfer (slope = -0.74 mole/kcal).65 Also, only small polar solvent effects were observed for the charge trans- fer quenching rate; (a factor of 2 in acetonitrile compared to benzene). A 13-fbld increase in the fluorescence quenching rate for a correspond- ing process involving full electron transfer was reported.66 Many studies indicate that full electron transfer is not involved in charge transfer complex formation between carbonyl triplets and amines. The small polar solvent effects and the decreased slopes of log kCT versus IPD plots suggest that at most only approximately 20% electron transfer is involved in the charge transfer complex formation.64a’67’68 69 Bartholomew gt_g1, later conducted flash studies on the photoreduc- tion of benzophenone with tertiary amines and found that a charge transfer complex forms in acetonitrile solvent; an exiplex may be 70 fermed in less polar solvents. Shaefer and Peters used picosecond absorption techniques to confirm the initial formation of radical 17 ions from benzophenone and triethylamine in acetonitrile, followed by either proton transfer to form the benzhydrol and amine radicals or decay back down to ground state molecules. Also, Amouyal and 7] used laser flash absorption techniques to investigate Bensasson the photoreaction of triplet duroquinone with tertiary amines and proposed that an exiplex is initially formed in both polar and non- polar solvents, followed by the formation of a charge transfer com- plex in solvents of high dielectric constant. The rate of charge transfer interaction between tertiary amines and carbonyls is fast, since these donors have relatively low ioniza- tion potentials.72 Tertiary amines undergo charge transfer complex formation with n,n* triplets of ketones such as benzophenone and acetophenone at nearly diffusion-controlled rates, leading to both quenching and radical formation.57"73 Mueller74 quenched the type II photoelimination of many ring-substituted valerophenones with tri- ethylamine in both benzene and acetonitrile solvents and observed diffusion-controlled quenching rates for those ketones with rela- tively low reduction potentials. Also, Wagner and Kemppainen75 reported an order of magnitude decrease in the quenching rate of .valerophenone with triethylamine in methanol as compared to benzene and acetonitrile solvents. The decrease was attributed to the de- creased availability of the hydrogen-bonded lone-pair electrons on the nitrogen atom. In addition to amines, other types of compounds are suitable electron donors for excited ketones. Kochevar and Wagner76 have investigated the quenching of the type II photoelimination of 18 butyrophenone with a wide variety of olefins and determined that charge transfer quenching predominates for electron-rich olefins, while energy transfer quenching is dominant for electron-deficient 77 reported that in the photoreduction olefins. Wagner and Leavitt of a-trifluoroacetophenone with alkylbenzenes, both charge transfer complex formation and direct hydrogen abstraction are involved. Cohen and Guttenplan78 determined that thioethers quench the triplet benzo- phenone in benzene and acetonitrile (kCT m 107 - 109 M'1 5"), but at a slower rate than tertiary amines, since sulfides have higher ioniza- tion potentials than tertiary amines. Also, both aromatic and ali- phatic mercaptans quench the phosphorescence of benzophenone with rate constants between 107 - 109 M'1 5'], respectively. In addition, ‘phosphorus, antimony, arsenic, and bismuth are thought to quench the type II photoelimination of butyrophenone by a charge transfer mechan- ism.50 Thus, charge transfer complex formation is a common type of interaction between molecules capable of donating or accepting addi- tional charge in the excited state. b. Intramolecular - Due to the limited number of conformations possible in bifunctional molecules, the study of intramolecular charge transfer interactions in these compounds can provide insight into the structure of the CT complex and the differences in charge trans- fer interactions with n,h* and n,n* triplets. In the past decade a number of studies concerning intramolecular charge transfer complex fbrmation have been published.73’75’79'84 The photochemical reaction of dialkylphenylacylamines was used as 19 a synthetic route to 3-hydroxyazetidines in only modest yields (9-22%), since type II photoelimination products (30-55% yields) were also ob- tained.79 80 Later, Padwa and coworkers investigated two N,N-dibenzyl- phenacylamines having either an n,n* or n,n* lowest triplet and found 1 [cu-12m I \cwzph —'-‘V——p + PhCH=NCH2Ph n ‘wflwene~ ll==ti,F!i similar type II quantun yields (on = 0.14 and 0.12, respectively) in ethanol. The lack of quenching by 1,3-cyclohexadiene and piperylene and the low type II quantum yields suggested that a charge transfer complex was fonmed at a rate exceeding diffusional quenching followed 20 by either back electron transfer to regenerate starting ketone or . proton transfer to generate a 1,4-biradica1. Padwag_i_:_31_.81 found that 3-aroylazetidines, which possess either an n,n* or n,n* triplet, give only arylpyrroles as photoproducts in low quantum yields (o 4.0.1). The authors proposed the rapid fbrmation of a charge transfer complex, fellowed by proton transfer and electron reorganiza- tion to form a biradical, bond closure, and elimination of water to give the observed products. The corresponding hydrochloride salts were found to be photochemically inert, since the nitrogen lone pair is no longer available. Thus, it appears that both n,n* and n,n* triplets can undergo charge transfer interactions. Wagner and coworkers73’75 investigated the photoreactions of a,y, and 6-dia1kylaminoketones in a variety of solvents. The inter- system crossing yields for these ketones are less than unity, with n: 1,3,4 21 lower values for decreasing values of n (AISC m 0.01 for n = l in benzene or acetonitrile). When n = 1, an unquenchable singlet state is responsible for all the photoelimination in benzene and aceto- nitrile and two-thirds of the photoelimination in methanol. In contrast, the photoelimination in compounds where n = 3 or 4 results from direct triplet-state y-hydrogen abstraction. Rapid intra- molecular charge transfer quenching is a competitive triplet-state process which results in deactivation of the triplet state to form ground-state ketone. Charge transfer quenching is 3.5 times faster for n = 3 than for n = 4, and five times faster in benzene or aceto- nitrile than in methanol. Since charge transfer quenching of the triplet does not result in biradical formation, the nitrogen lone pair must be held near the carbonyl and the y-hydrogens away from the carbonyl moiety in the charge transfer complex. 67 also investigated 4-benzoyl-4,N-dimethyl- Wagner and Scheve piperidine (n,n* lowest triplet) in which the nitrogen lone pair is held approximately 4-6 A from the carbonyl group. The two possible conformers formed distinct, non-interconverting triplets: the triplet having the benzoyl group axial underwent rapid y-hydrogen abstraction, fbllowed by cyclization of the 1,4-biradical, while the triplet having the benzoyl group equatorial underwent only a-cleavage. When the nitrogen lone pair is axial, the relative orientation and overlap of orbitals is poor and charge transfer quenching does not occur. The rate constant for CT quenching of the other triplet cannot exceed 2x1061 5' . This rate is slower by a factor of 103 as compared to the rate of CT quenching in the acyclic y-amino ketones.77 From these 22 31.¢ 11* 3" 1* L ‘Me‘ .9" l l ., 4. i“ g .t results the authors concluded that CT quenching in acyclic y-amino- ketones occurs solely by through-space rather than through-bond inter- actions. Wagner and Ersfeld67’82 photolyzed B-naphthyl-y-dimethylamino- propyl ketone and found inefficient photoelimination (411 = 0.008) in both benzene and acetonitrile solvents due to a n,n* lowest triplet and efficient CT interaction between the triplet state and the amine. The authors proposed that the cyclic charge transfer complex formed must be restricted to conformations in which the hydrogens a to the nitrogen are kept away from the carbonyl such that 1,5-proton transfer cannot occur. In contrast, bimolecular photoreduction of triplet 23 naphthyl ketones by amines results in efficient radical formation.83 In methanol the photoelimination proceeds at moderate efficiency (all s 0.17) and it was suggested that protonation of the oxygen atom in the CT complex by methanol leads to diradical formation and type II photoproducts.82 84 Winnik and Hsiao studied a series of benzophenone derivatives in which the benzophenone chromophore and an ethenyl moiety were separated by one to nine methylene units and found significant intra- molecular quenching of benzophenone room temperature phosphorescence emission when n = 9. The authors concluded that charge transfer quenching occurs only when the double bond approaches a van der Waals distance from the benzophenone carbonyl moiety and that CT quenching involves electron transfer to the electron deficient n orbital loca- lized on the carbonyl oxygen. Later experiments perfbrmed by Mar and Winnik85 with an extension of the methylene chain showed an in- crease in the quenching rate until n = 12, and then a rapid decrease in quenching (n = 13 to 21) due to the rapid increase in the total number of chain conformations as compared to the only modest increase in the total number of chain conformations which lead to quenching. Thus, these experiments suggest that a specific geometry is required in order for efficient charge transfer to occur. 24 86 Masuhara t 1. used laser spectroscopy to study systems in which benzophenone and N,N-dimethylaniline are connected by a methylene n==1;2;3 chain. The transient absorption spectra observed in acetonitrile could be reproduced by superposition of those of the benz0phenone anion and DMA cation, and the spectra in benzene were similar to those of the benzophenone ketyl radical or triplet benzophenone. Thus, the authors proposed that intramolecular hydrogen abstraction resulting in the formation of benzophenone ketyl radical occurred in benzene whereas intramolecular electron transfer occurred in aceto- nitrile, and both processes were almost completely independent of the number of methylene units. Thus, they concluded that a definite, restricted structure was not necessary for electron transfer or hydrogen abstraction, since these processes occurred rapidly both in a loose structure (n = 1,2) or in a sandwich-type structure (n = 3). These results contradict those of previous researchers and seem suspect to error, since when n = l the lone pair on the amine cannot possibly come close to the carbonyl and the possibility for intramolecular hydrogen abstraction seems remote when n = 1. Thus, many unanswered questions still remain concerning the con- fbrmational requirements involved in charge transfer complex formation. 25 E. Stern-Volmer Kinetics Phenyl alkyl ketones undergo Norrish Type II photoelimination by y-hydrogen abstraction to give a 1,4-biradica1 which then undergoes cleavage, cyclization, or disproportionation back to ground-state ketone (Scheme 1). The triplet lifetime, 1, is dependent on both the rate constant for y-hydrogen abstraction, kr’ and the rate constant for radiationless decay, kd (Equation 9). _ -1 T ' (kr + kd) (9) Quantum yields for type II photoelimination are determined by competitive excited state reactions and by partitioning of the bi- radical: (10) where AISC is the quantum yield for intersystem crossing, kr is the rate constant fbr y-hydrogen abstraction, and P is the probability p that the biradical will go on to form product. The addition of a Lewis base usually results in solvation of the biradical, thus in- hibiting disproportionation back to ground-state ketone, and conse- quently maximizing the type II quantum yield (Equation 11). ' k ' T (11) 87 Stern-Volmer quenching kinetics can be used to determine 26 triplet lifetimes: o°l¢ = kq - T ° [0] + l (12) where 4° and a are the quantum yields for acetophenone formation in the absence and presence of external quencher, respectively and kq is the rate constant for bimolecular quenching by external quencher, Q. Intersystem crossing yields can be determined by using the ketone to sensitize a well-known triplet reaction, such as the cis + trans isomerization of 1,3-pentadiene: -1 g -1 1 sens ¢ISC (1 + kq - T - {03’ (13) oi°Pem eeeee.ene=m z.e x =.e 3 PI PI m .mmcocmgaogmpm> umpzuvumnzmimcva Low msmumEugnm ovumcpxouo;m .p mpnmh 33 .gmppmaz .m conga: an mapamme um;m_—n=a:= : a .uamuemu:.\maopm n p gm .mu oucmemmwm ease mwspa> a .nnn mo copm_umgq wmugm>a ;a_3 was; ououwpazv we mango>m appaamzm .mcm~:wn :p ago?» Ezucmzc moccsamaammpo u .eeeeeese : o._ a» z m.c ee.3 unneeexee ape.» eeeeeecd .cowumsgom mcocmnqoumua com upowx Espcmacn .copmgm>:ou Nopim on E: mpm an vagueness? macaw; z wo.ow emm em. ---- em.c eom.o eedneem mau-e emnem ee_ ---- e~.o em~.o eednedm «20-5 eo_nmm can ---- cm.o eo~.o eeeneem mdo-e ---- omnomm ---- ---- Po.cnmo.o dennede m:uou-a dAszwv eAeeenwv x-e xeee HHe eed>_em eee:e.eme=m 2;; Eex e a PI .edaeeeeeu ._ deeee Table 2. Photokinetic Parameters for Phenyl Alkyl Ketones Function of y-Substitution.a ‘scwzcuzaimnz x R1 R2 311 -dmax~ de,M-] 1/t,107s"1 H H H 0.23 ---- 550c 1.3 H H CH3 0.33d 0.85 47:1 11. H CH3 CH3 0.25d 0.90 10c 50. CN H H 0.12 0.31 400240 2.5 CN H CH3 0.17 0.47 74:1 5.7 cu CH3 CH3 0.13 0.47 18 23. a0.04 M ketone in benzene irradiated at 313 nm to ~10% conversion. b formation. cValue in Reference 15 is 625. dValues taken from Reference 15. Values determined from Stern Volmer runs monitoring acetophenone 35 6.0 - 5.0 " 4.0 r ‘0 O O \ \o 1.0 1 l l l l 0.02 0.04 0.06 0.08 0.1 0 101, M Figure 2. Stern Volmer Plots for Substituted Valer0phenones in Benzene with Diene Quencher (OH;.o-CN;Am-CN;Ip-CN). 6.0 5.0 4.0 6- o 3.0 Figure 3. 36 0.02 0.04 0-06 0.08 101ml Stern Volmer Plots for Substituted Valerophenones in Aceto- nitrile with Diene Quencher (OH;.0-CN ;Am-CN;Ip-CN). 37 ' I I. 'I (I A 2.0 ' 0 I A 1° ¢ ‘ V D 1;) a 1.0 0.02 0.04 0.06 0.08 101,M Figure 4. Stern Volmer Plots for Substituted Valerophenones in Benzene with Diene Quencher (Oo-COZCH3;D m-CDZCH3; 38 A I 3.0 - ‘3 IA 0 1:1 qbo ¢ I A I 2.0 (- IA ’1 (D A . ‘ A I, ' 1.0 I 4 1 a l 0.0 0.02 0.04 0.06 0.08 0.1 0 [OLM Figure 5. Stern Volmer Plots for Substituted Valerophenones in Acetonitrile with Diene Quencher ( O o-COZCH3;E] m-CDZCH3; 39 D 4.0 " ’l . d>° 3.0 - cp O H 0 A 0 2.0 - 1‘ ’ A' I A. I y 1.0 1 L 4 L 1 l 0.0 0.02 0.04 0.06 lQl.M Figure 6. Stern Volmer Plots for Substituted Valerophenones in Benzene with Diene Quencher (Ap-CDCH ;E]p-C0C4H9; o m-COC4H9;. m-C0C4H9 in acetonitrilg). (Figures 7-12). In those cases where the intercept was below 1.0, qu was determined by dividing the lepe by the intercept. The values obtained are also included in Table l. 2. anntum Yields Quantum yields for acet0phenone formation were determined by parallel irradiation at 313 nm of 0.04 M ketone solutions and usually benzene solutions of 0.1 M valerophenone as actinometer in a merry- go-round apparatus.9] All samples were degassed prior to irradiation and conversion was usually kept below 10%. In all cases both the ketone solution and the actinometer absorbed all the incident irradia- tion. The values are included in Tables 1 and 2. 3. Maxim Quantun Yields Maximum quantum yields for acetophenone formation were obtained by adding various amounts of Lewis bases to 0.04 M ketone solutions in benzene. For most ketones a maximum quantum yield of unity f0r total product formation could not be attained, since the addition of Lewis base up to a certain value maximized the quantum yield and further Lewis base either had no effect or slightly decreased the quantum yield. The values are given in Tables 1 and 2 and Figures 13 and 14 show the effects of added pyridine, t-butyl alcohol, and dioxane on the Type II quantum yield for p-cyanovalerophenone. 41 a 5L1) ' A El /A qbo» -— 2.0 F o 9’ ' o 0.04 0.08 0.12 101." Figure 7. Stern Volmer Plots for Substituted Valerophenones in Benzene (0.5 M Pyridine) with Triethylamine Quencher (O H;Um—CN;Ap-CN). 9. 3.0 2.0 1.0 ' Figure 8. 42 Q Q 7 l '1 r ‘ f5- 0.04 0.08 0.12 101. M Stern Volmer Plots for Substituted Valerophenones in Acetonitrile with Triethylamine Quencher (O H;E] m-CN; Ap-CN). ~e. Figure 9. 3.0 2.0 1.() 43 ’D >\ '0 ‘.> 0 \J> I l l l 0.04 . 0.08 101, M Stern Volmer Plots for Substituted Valerophenones in Benzene (0.5 M Pyridine) with Triethylamine Quencher (o o-0020H3; |'_'_] m-0020H3;Ap-0020H ) 3 O 0.12 44 6.0 - A 5.0 - 4.0 - ——-1T “~‘ ,,,, ‘— 7 . n-br’ . ------ n * _ --------- ~ ~“ fl ‘ ~ 8 ” s~~ ‘~‘§ . s ‘\ ~ ~ — ‘\~~ ”——’-‘-—_"' 7 §-- 1 —_ Scheme 4. Mixing of h-Orbitals in Benzoyl System. 79 transition negligible (Scheme 4). Another (-R) substituent reinfbrces this orbital splitting, since inductive effects on transition dipoles greatly affect the 3La energy level. The vector addition of individual substituent dipoles for 1,4-acceptor, acceptor substituents results in greater stabilization than does a similar 1,3 pair. The M0 orbital diagram indicates that a para substituent should lower the n,n* triplet by the same amount as the first substituent; whereas, a meta substituent should lower the triplet energy by only 1/4 the amount, if the spin density at-the site affects the amount of stabilization affbrded by the substituent. The n,n* triplet energies measured for substituted benzonitriles and methyl benzoates seem to corroborate this simple M0 representation of the h,n* triplet. The valence bond representations below describe the La n,n* triplet of phenyl ketones. x 'i The most important resonance f0rm is the 1.4-diradical “quinoidal” ferm of the triplet.98 EPR studies99 showed that very little charge density lies at the meta position, as is depicted in the middle valence bond structure. The third structure represents a high-energy charge-transfer state which mixes somewhat with the low-lying 3La 80 1 103 state but to a greater extent with the high-energy La state. For phenyl alkyl ketones containing substituents capable of conjuga- tion with the ring, the following valence bond structure depicts a folly conjugated h-system. Thus, significant contribution of this structure, or the analogous ortho-structure, would account for the significantly larger stabiliza- tion of the n,n* triplet afforded by 0- and p-CN, p-COZCH3, and p-COR substituents as compared to the model CF3 substituents. As long as the n-orbital remains orthogonal to the n-system, an n,n* transition can be regarded simply as a one-electron reduction ‘04 EPR studies105 of the n-system. on benzonitrile radical anions indicated that the additional electron density in the benzene ring occupies primarily the l- and 4-positions with negligible spin density at the meta position. Thus, substituents have diminished effects in the meta position. Valence bond representations of the n,n* triplet are shown below. 81 Electron-withdrawing substituents inductively stabilize the n,n* triplet. The substituent effects determined for benzophenone n,n* triplets confirm the larger stabilization provided by para- versus meta-substitution by electron-withdrawing substituents. E. Type II anptgm Yields The Type II quantum yields in benzene, wet acetonitrile, and in benzene with added Lewis base for these substituted valer0phenones are given in Table l. The quantum yields for most ring-substituted valerophenones can be maximized to unity with added Lewis base as long as there are no competing triplet processes. The Lewis base hydrogen bonds to the hydroxy proton and prevents disproportionation from occurring.10b The quantum yields for these conjugatively electron-withdrawing substituted valerophenones rises to maximum values considerably less than unity with added Lewis base (i.e., pyridine, t-butyl alcohol, or dioxane) as shown in Figures 13 and 14. The quantum yields in wet acetonitrile are generally higher than with added Lewis base. The inability to sufficiently maximize the quantum yield is dif- ficult to explain, since electron-withdrawing substituents increase the acidity of the hydroxy proton. Thus, these biradicals must be completely solvated by the added base, but for some reason do not always go on to form product. One plausable explanation involves resonance stabilization of the solvated biradical which would perhaps make disproportionation competitive with product formation. 82 Polar solvents or Lewis bases would stabilize such charge separation. Since the possibility remains that some other triplet decay process, kd, could be competitive with y-hydrogen abstraction, kr’ 28 suitable experiments as in the case of p-methoxyvalerophenone, were conducted in order to determine kd values. Only if y-hydrogen abstraction is found to be the only triplet process can one equate 1/1 with kr' F. Determination of k, Values by Various Methods The rate of y-hydrogen abstraction is dependent on changes in the y-C-H bond strength.‘5:23"°“ Table 2 lists quantum yields in benzene, maximum quantum yields with added pyridine, and qu values for both unsubstituted and p-cyanosubstituted butyrophenones (1°y-H), valerophenones (2°y-H), and y-methylvalerophenones (3°y-H). In both series the y-methylvalerophenone is approximately f0ur times more reactive than the corresponding valerophenone. In contrast, butyro- phenone is much less reactive (factor of 6) than valerophenone, while p-cyanobutyrophenone is only 3 times less reactive than the corresponding valerophenone. The reason for the greater reactivity of p-cyanobutyrophenone than predicted by the unsubstituted models is not apparent, but appears to be real. The Type II quantum yield for acetophenone formation is determined 83 by competitive excited state reactions: “11 = “150 ' kr ' Pp ' T (1°) where °ISC is the quantum yield for intersystem crossing, kr is the rate for y-hydrogen abstraction, PD is the probability that the bi- radical will go on to form product, and T = (kr + kd)']. The inter- system crossing yields for both p-cyano and p-carbomethoxyvalero- phenones were measured and found to equal unity. Within each series of compounds both P and kd remain constant, since increased y-sub- stitution should no: affect these parameters. Since the quantum yields remain nearly constant within each series, whereas, the trip- let lifetimes decrease appreciably with increased y-carbon substi- tution, then an increase in the rate of y-H abstraction with increased v-carbon substitution must be responsible. Therefore, kd is not competitive with kr’ and kd must be less than 106 s']. In order to insure that kd is indeed smaller than kr’ bimolecular photoreduction experiments were conducted.. Photoreduction experi- ments on p-cyanoacetophenone using either toluene or p-xylene as donor and naphthalene as quencher in acetonitrile solvent indicate that kd = 4 x 105 5']. Thus, kd << kr and I/T can be equated to kr' Consequently, the exceptional inability to maximize the total quantum yield to unity for these (-R) substituted valerophenones must be due to the reduced ability of the intermediate biradical to go on to form product. 84 G. Ketone Photoreactivity and Calculation of Relative Triplet Energies It has been shown that the observed rate constant, kobs’ for ketones with n,n* lowest triplets is described as follows: k - kg” (3) obs = Xn,n where x",1r is the thermal equilibrium fractional population of the n,n* state and k3’" is the intrinsic rate of hydrogen abstraction for the appropriate n,n* triplet. The population of the n,n* trip- let at a certain temperature can be calculated from the Boltzmann equation as follows: AE/RT)-1 x =(l+e (l4) n,h I where AE is the energy separation between the two triplets and T is the temperature in degrees Kelvin. Thus, if one can estimate kg’", then calculation of the energy separation between the two triplets becomes possible. Trifluoromethyl groups increase the energy gap between the two triplets by stabilizing the n,n* triplet while having little effect on the 1r,1r* triplet such that population of the upper 11,1r* triplet is essentially zero. Since CN, 002R, and COR all have Hammett a values similar to that of CF3,107 .their intrinsic kg’" values must nearly equal kr for the analogous o-, m-, or p-trifluoromethylvalero- phenone. Since the rate of hydrogen abstraction is enhanced only 85 by a factor of 2-3 by the inductive effect of m- and p-CF3 on the electrophilic n,n* triplet, the error involved in estimating the other ka’" values must be negligible. From the Stern Volmer quenching studies and the other experi- ments verifying that y-hydrogen abstraction is the only process responsible for triplet decay, I/T = kgbs. The data from Table 1 indicate that p-C0C4H9, p-CN, and p-COZCH3 substituents decrease triplet reactivity to 10%, 25%, and 40%, respectively, as observed “for p-CF3 valer0phenone. From these xn,h values, the AET separations calculated are 1.3, 0.67, and 0.3 kcal/mole, respectively, in benzene at room temperature. Since I/T increases by an average of 50% at most in acetonitrile, then these values cannot be very different in acetonitrile. It is interesting that p-divalerylbenzene is twice as reactive as p-acetylvalerophenone. Although each compound has two chromo- phores capable of absorbing light, only excitation of the valeryl carbonyl can lead to y-hydrogen abstraction. Since both carbonyls have an equal probability of becoming excited, then the decreased reactivity of p-acetylvalerophenone reaffirms the idea that excitation in the n,n* triplet is localized primarily on the carbonyl. Both m-CN and m-CDZCH3 valerophenones show reactivities comparable to that of the model m-trifluoromethylvalerophenone. All three ketones have n,n* lowest triplets. Conversely, m-divalerylbenzene is only half as reactive as the model ketone, thus implying that the n,n* and n,n* triplets are isoenergetic and equally populated. The spectroscopic data seem to be in good agreement with this 86 assignment. The observed photoreactivity fer the ortho-substituted valero- phenones is more difficult to interpret, since steric factors are also involved. o-Cyanovalerophenone is twice as reactive and o- carbomethoxyvalerophenone is only 1/4 as reactive as the o-trifluoro- methylvalerophenone model. Unfortunately, o-CF3 valerophenone is not an ideal model since it displays decreased reactivity as compared to its meta and para isomers, presumably due to steric factors. Thus, calculation of the energy separation for the two ketones from the kinetics is impossible. From the spectroscopy o-cyanovalerophenone has nearly isoenergetic triplet levels; whereas, o-carbomethoxy- valerophenone has a definite n,h* lowest triplet. At least a quali- tative correlation exists between the observed reactivities and the energy separations predicted from the spectroscopic data. Thus, the photoreactivity of these ketones prevides a more sensi- tive method for determining the energy separation between the two triplets. In general, both photochemical and spectroscopic data agree that p- (-R) substituents stabilize the n,n* triplet to such an extent that these ketones possess n,n* lowest triplets. H. Attempted Correlation of Reactivities with Hammett 6 Values Wagner et 31.29 have correlated the relative rates of y-hydrogen abstraction of ring-substituted phenyl ketones with Hammett o param- eters (Figure 27). Both meta and para inductively electron-with- drawing (-I) substituents (n,n* lowest triplets)(dashed line) and weakly electron-donating substituents (m-, or p-CH3, -0CH3) (n,n* 87 00 9 / O/ / / 90e 0 9 El 0 9 'ogkobs-1.0 -42JO 4 A L Figure 27. Plot of Relative k b5 Values as a Function of Ground State Hamett o VaTues.o -,I Substituents;0, Electron- donating Substituents;e, para-R Substituents;., p- -Cl; U , p-SCF3o 88 lowest triplets) (solid line) gave linear correlations with dif- ferent slopes. p-Cl did not fit on either line, nor does our p-CN, 108 29 I p-COZCH p-COR, and m-COR, or p-SCF3. As already pointed out, 3. a Hammett plot is inappropriate f0r ketones with n,n* lowest triplets where kobs values are dominated by Boltzmann factors rather than by substituent effects on actual kc’" values. Also, since Hammett constants do not adequately describe substituent effects on n,n* triplet energies, then “ET values cannot Correlate with Hammett substituent constants. Ground state a values decrease in the order CN > COR > CDZCH3, whereas, conjugative effects on n,n* triplets dis- play a different order: COR > CN > COZCH3. The coplanarity of the excited benzoyl groups compared to the twisting of the ground states94 would explain the greater conjugating ability of acyl groups in the excited state. I. Chppge Transfer Quenchipg Studies Substituted phenyl alkyl ketones can undergo charge transfer interactions with tertiary amines. 61 65 The equation developed by Weller and later modified by Cohen for carbonyl compounds describes the relationship between the rate 89 constant of charge transfer quenching and the various parameters affecting the change in free energy involved. log kcT a. AGCT n. IPD - E(A'/A) - ABEO’O + c (8) Since in all the experiments triethylamine was used as donor, then IPD remains constant, as does C. Thus, if one can determine both the reduction potential and the energy of the triplet involved for the acceptor, then one can calculate relative AGCT values. From comparison of diene and triethylamine quenching rates under similar conditions, one can determine the rates of charge transfer quenching from the following equation: k T(Et N) k=“3-k (15) CT quIdiené) q 9 M"1 s'1 in benzene where kq is the rate of diene quenching (5 x 10 and 1 x 1010 M’1 s'1 in acetonitrile). Table 9 contains the values of kCT in both benzene and acetonitrile solvents. The parameters neces- sary to plot log kCT versus excited state reduction potential (Figure 28) are summarized in Table 10. Assuming that the rates of charge transfer quenching of the n,n* and n,n* triplets are not significantly different,83 then the energy of the lowest triplet was used in cal- culating the excited state reduction potentials for the graph. Even if this assumption proves to be erroneous, then only small errors are involved since most of the ketones studied possess n,n* and n,n* triplets in close proximity. 90 Table 9. Charge Transfer Quenching Data for Substituted Valerophenones. Substituent Solvent k", 107s" kCT, 109s" H Benzene 11. 1.2 H Acetonitrile 16. 2.1 o-CN Benzene 23. --- o-CN Acetonitrile 30. -- m-CN Benzene 26. 5.8 m—CN Acetonitrile 50. 5.0 p-CN Benzene 6.8 6.1 p-CN Acetonitrile 11. ll. o-COZCH3 Benzene 3.6 2.2 o-COZCH3 Acetonitrile 3.0 2.5 m-COZCH3 Benzene 28. 6.9 m-COZCH3 Acetonitrile 48. --- p-COZCH3 Benzene 12. 5.5 p-COZCH3 Acetonitrile 17. 16. m-COC4H9 Benzene 14. 3.8 m-COC4H9 Acetonitrile 22. 7.2 p-COC4H9 Benzene 2.7 --- p-COC4H9 Acetonitrile 1.4 --- o-CF3 Benzene 13.a 7.2 m-CF3 Benzene 32.a 8.4 p-CF3 Benzene 28.a 15. p-CF3 Acetonitrile 42.a 21. aUnpublished results by Warren 8. Mueller. 91 10.4 " 10.0 - IOQ kc-r T 9.2 - L 1 l l 1 1.0 1.2 1.4 ' * 'Ered,eV Figure 28. Correlation of Charge Transfer Quenching Rates for Sub- stituted Valer0phenones in Benzene (0.5 M Pyridine) with Excited State Reduction Potentials: O n,ii* lowest Triplet; Un,n* Lowest Triplet. 92 Table 10. Charge Transfer Quenching Parameters in Benzene. k ET ET CT 109 Substituent (n,n*) (n,n*) 'Ereda '*Ered(ev)b 109s'] kCT H 73.4“ 75 5“ 47.7 1.11 (1.21) 1.2 9.1 o-CN ~7l.6 71.0 37.8 1.47 (1.44) --- --- MPCN 73.3 73.8 40.9 1.41 (1.43) 5.8 9.8 p-CN 71.2 59.3 35.3 1.51 (1 43) 5.1 9.8 o-0020H3 73.4 71.5 44.5 1.25 (1.17) 2.2 9.3 n-coch3 73.6 74.5 43.8 1.29 (1.33) 5.9 9.8 p-0020H3 71.5 70.3 37.5 1.47 (1.42) 5.5 9.7 m-COC4H9 73 4573 42.8 1.31 (1.31) 3.8 9.6 p-C0C4H9 71 57.7 35.7 1.53 (1.39) --- --- o-CF3 m 73 73.0 43.8 1.27 (1.27) 7.2“ 9.9 m-CF3 72.8 74.7 42.9 1.30 (1.38) 8.4“ 9.9 p-CF3 72.4 74.3 40.6 1.38 (1.46) 15.“ 10.2 aVal ues in kcal/mole. bValues for excited state reduction potentials f0r n,n* triplets; values in parentheses for n,n* triplets. cValues taken from Reference 29. dUnpublished results by Warren 8. Mueller. 93 Weller's equation seems to hold for these (-R) substituted valerophenones. In all cases these compounds possess excited state reduction potentials lower than valerophenone itself and exhibit increased rates of charge transfer quenching. The rate of charge transfer quenching generally increased at most by a factor of 2 in acetonitrile. As previously determined, the separation between the two triplets cannot be significantly different in acetonitrile than in benzene. The rate of charge transfer quenching with tri- ethylamine exceeds the rate of diene quenching for many of these (-R) substituted valerophenones. In summary, these electron-withdrawing substituted valerophenones readily undergo charge-transfer interactions with tertiary amines, many at rates which approach diffusion control. Since the n,n* and n,n* triplets are close in energy and the triplet energies are estimated values, then correlation of the rates of charge—transfer quenching with the nature of the triplet undergoing the interaction is impossible. All Stern Volmer quenching experiments involving triethylamine in benzene solvent contained 0.5 M pyridine to solvate the biradical. For many ketones it is apparent that small amounts of triethylamine (pK; solvate the biradical to a greater extent than does pyridine (pKa = 5.2)]09, since slightly more photo- product was produced in the lowest concentration quenched tubes than in the unquenched tubes. 94 J. Correlation of Reduction Potentials with Hammett a Values Nadjo and Saveant96 have related the reduction potentials of substituted acet0phenones, fluorenones, and benzophenones to Hammett oIn and op parameters. A similar correlation was sought fer the wide variety of substituted valerophenones studied. The reduction po- tentials and Hammett 0 values for both meta and para substituted ketones are presented in Table 11. A plot of "Ered versus am or 0D values (Figure 29) gave a linear correlation which suggests that resonance effects are indeed important in stabilizing the radical anion formed by the one-electron reduction of phenyl ketones. When Hammett op values were used instead of Op- values, the reduction po- tentials of p (-R) ketones fell well below the line. The only anomalies found were the COZH and C02" substituted valerophenones which fell symmetrically about the line. Perhaps acid or base catalyzed reactions with the solvent or reduction of the carboxy functionality are responsible. Whatever the explanation for these discrepancies, the other ketones seem to correlate very well with Hammett parameters. K. Correlation ofippn* Triplet Energies for Substituted Phenyl Ketones with Hammett 0 Values d89 has published several correlations of n,n* triplet Arnol energies for both substituted acet0phenones and benzophenones with Hammettom and op values. The acet0phenones gave a good linear correlation (no -R substituents were included). The benzophenones 95 Table 11. Correlation of Hammett a Values with Reduction Potentials for Valerophenones. Substituent cm or op“ op‘ “ -Eredb H 0 47.7 mPCN l +.56 40.9 p-CN ~ +.66 +.90 36.3 1500ch3 +.37 43.8 p-COZCH3 +.45 +.68 37.5 m-COC4H9 +.38 42.8 p-000H3 +.50 +.87 35.7 m-CF3 42.9 p-CF3 +.54 40.6 m—CH3 -.07 48.0 p-CH3 -.17 49.7 m-OCH3 +.12 47.3 p-OCH3 -.27 -.2 51.0 m-F +.34 44.5 p-F +.06 ‘ -.02 48.1 m-Cl +.37 43.9 m—COZ' -.10 42.9 p-COZ' 0 40.9 m-COZH +.37 49.7 p-COZH +.45 +.73 47.0 aValues taken from Reference 107. bValues given in kcal/mole. 96 52 - 48 :- 'Erod (koal/ 44 ' 1110101 40 r 3.6 D (:1 -0.1 0.1 0.3 0.5 0.7 0.9 amid-p- Figure 29. Correlation of Half-wave Reduction Potentials for Sub- stituted Valerophenones with Hanmett “m and op" Values: 0 meta-Substi tuti on; C1 para-Substi tuti on . 97 (both mono- and symmetrically substituted compounds) did not correlate well with the additive Hammett parameters for disubstitution (Figure 30), but a somewhat better correlation can be obtained when Hamett am and a; values are used and symmetrically substituted benzophenones are treated as monosubstituted compounds (Figure 31). Arnold89b later studied a wide variety of both mono- and symmetrically and unsymmetri- cally substituted benzophenones. They found that all the symmetric derivatives correlate fairly well with a Hanmett two-parameter treat- ment employing both a and 0' values, indicating that both polar and radical-stabilizing effects influence the n,n* triplet state. For un- symmetrically substituted benzophenones, the triplet energies were 110 lower than predicted, presumably from merostabilization from substi- tuents that can stabilize charge separation in the free spin system. L. Correlation of nin* Triplet Energies with Reductioanotentials In 1973 Loutfy and Loutfy92 published a correlation between n,n* triplet energies and half-wave reduction potentials for substituted acet0phenones. Also, similar correlations were published for substi- 89b and thiophenes.97 Since the n-orbital is orthog- tuted benzophenones onal to the n-system, substitution of a group into the phenyl ring would not affect the energy of the n-orbital but would affect the energies of both the n and 5* levels.104 Loutfy maintains that p- cyanoacetophenone has a lowest n,n* triplet, since it lies on the line 98 (kcal/ mole) -O.4 O 0.4 0.8 1 .2 (Tm 9 Up Figure 30. Correlation of n,n* Triplet Energies (4:1 MCH/IP, 77°K of Substituted Benzophenones with Hammett Parameters.89a U , I (-R) Substituents... Values Added From This Study. 69" ET 68 (kcal/ mole) 67- l 1 1 I L _1_ -0.2 0 0.2 0.4 0.6 0.8 cm 9 Up- Figure 31. Correlation of n,n* Triplet Energies (4:1 MCH/IP, 77°K) of Substituted Benzophenones with Hanmett Parameters: U ,I (-R) Substituents;o, [JValues Taken From Ref. 89a. 99 formed by -H, p-Cl, p-Br, and p-CF3 substituted acet0phenones. Since the triplet energy for p-cyanoacetOphenone was measured in ethanol glass, while the other ketones were measured in 4:1 methylcyclohexane/ isopentane glass, we measured the triplet energy for p-cyanoacetophenone in a comparable glass and found it to be only slightly lower (0.5 kcal) than the reported value in ethanol. In contrast, our study involving both spectroscopic and photokinetic data suggests that p-cyanovalero- phenone (therefore p-cyanoacetophenone also) has a n,n* lowest triplet. In order to probe the matter further, a similar correlation was attempt- ed on a wide variety of substituted valerophenones in both a fluid glass (isopentane) and a more rigid and polar glass (ethanol) at 77°K (Figures 32 and 33). It appears that in both isopentane and ethanol glasses, most of the ketones with n,n* lowest triplets fall on a line and those ketones with n,n* lowest triplets fall below the line. The most noticeable exceptions are o-CN and m-COC4H9 in isopentane glass, since they are predicted to have nearly isoenergetic energy levels by the other methods. In general the energy separations between the n,n* and n,n* triplets predicted by this correlation are much larger (iso- pentane glass) than those previously estimated in benzene at room tem- perature. Fortunately, the Boltzmann equation (Equation 1) would pre- dict a somewhat larger energy separation at lower temperatures, and also, n,n* triplets in solution are generally lower by approximately 2 kcal than in rigid glasses due to differences in conformation between the ground state and the excited state.93 It appears that Loutfy's correlation is at least qualitatively correct in most cases, and gives a rough estimation at best of n,n* triplet energies. 100 761- I ET’ II (kcaU' ‘58 ' flung) II - In I “4 I l l 1 1 L l l 1.6 1.8 2.0 2.2 Figure 32. Attempted Correlation of n,n* Triplet Energies (Iso- pentane, 77°K) with Halfewave Reduction Potentials for Substituted Valerophenones: C) n,n* Lowest Triplets; [j'n,n* Lowest Triplets. 101 68 F ' II 64 .'. 1 .1 I i I I I L l 1.6 1.8 2.0 2.2 ‘Erod,ov Figure 33. Attempted Correlation of n,n* Triplet Energies (Ethanol, 77°K) with Half-wave Reduction Potentials for Substituted Valerophenones: O n,ir* Lowest Triplets; I11,1r* Lowest Triplets. PART II REGIOELECTRONIC CONTROL OF INTRAMOLECULAR CHARGE TRANSFER QUENCHING IN VARIOUS PHENYL KETONES 102 RESULTS A. Photokinetic Studies 1. Stern-Volmer Quenching Studies In general 0.01 M ketone solutions containing varying amounts of quencher in benzene or wet acetonitrile (2% H20) were irradiated at 313 nm to 5 - 10% conversion (acetophenone photoproduct was measured). A linear correlation was obtained for Stern Volmer quenching plots of ¢°/¢ versus quencher concentration (Figures 34, 35 and 35). The slope is equal to k T, where T is the triplet life- q time of the ketone. The triplet lifetimes can be calculated, since 91 s' in benzene and l x 10 M- s' in aceto- nitrile. Duplicate runs usually agreed to within 10% of each other. Table 12 contains the photokinetic data for the model com- pounds and Tables 13 and 14 contain the data for the amino-ketones studied. Also, Figure 37 depicts the extrapolation of triplet life- times to infinite dilution in order to eliminate intermolecular CT processes (both lines must have similar slopes since intermolecular CT quenching rates are approximately the same). The phosphorescence lifetimes for the model m- and p-carbo- methoxybenzophenones and p-2BB (1 x 10'4 M) were measured by diene quenching of the phosphorescence emission in carbon tetrachloride solution at room temperature (Figures 38 and 39). Also, emission 103 104 I 3.0 L- I .4 2.0 L C] ¢O <5 1.0 0.02 V 0.06 0.10 0.14 [OLM Figure 34. Stern Volmer Plots for Diene Quenching of 0.020 M Ketones: 0 p2VB in Benzene;. p2VB in Acetonitrile; ‘p3VB in Acetonitrile; DmZVB in Benzene; and I m2VB in Acetonitrile. 105 4.0 r 3.0 - . (pa Cb 2.0 L 1.0 4.0 8,0 ‘ 12.0 [01,10‘4111 Figure 35. Stern Volmer Plot for Diene Quenching of 0.020 M p3VE in Benzene. 106 I L 1 I 1.0 2.0 [01." Figure 36. Stern Volmer Plot for Diene Quenching of 0.020 M p- Me03E in Acetonitrile. 107 Table 12. Photokinetic Data for Valerophenone Models.a "Q—(Lr -X Solvent Q IIIg Amax qu p-COZCH3 .Benzene Dieneb 0.19 0.33 42:2 p-coch3 Benzene“ Amine“ ---- ---- 32 p-0020H3 Benzene“ Amine: ---- ---- 25 p-COZCH3 Acetonitrile Diened 0.60 ---- 5825 p-COZCH3 Acetonitrile Amine ---- ---- 4020.5 p-0020H3 Acetonitrile Amine“ ---- ---- 47 m-coch3 Benzene Dieneb 0.25 ---+ 18:1 m-COZCH3 Acetonitrile Dieneb 0.90 ---- 21:1 m-COZCH3 Acetonitrile Amine“ ---- ---- 8.0 p-OCH3 Benzene Dieneb 0.11 ---- 4,300:500 p-OCH3 Benzenec Aminef -—-- ---- ~501 p-00H3 Acetonitrile Dieneb 0.21 0.25h 6,400:400 p-OCH3 Acetonitrile Aminef ---- ---- 202 a0.040 M ketone solutions irradiated at 313 nm to 5_10% conversion. b2,5-Dimethylhexa-2,4-diene or 1,3-pentadiene. c0.50 M Pyridine added. dB-Dimethylaminoethyl benzoate. ey-Dimethylaminopropyl benzoate. fN,N-Dimethylaminopropyl phenyl ether. gUsually 0.10 M solutions of valerophenone in benzene used as acti- nometer; formation of acetophenone monitored. h Value from Reference 28. 1Value estimated from solvent effects on quenching p-methoxyvalero- phenone with triethylamine obtained by Warren 8. Mueller. 108 Table 13. Photokinetic Data for Amino-Esters.a rib-U Name Position R Solvent bub quc p-2VB para -(CH2)2N(CH3)2 Benzene“ 0.07 10. p-ZVB para -(CH2)2N(CH3)2 Acetonitri1ee 0.12 14.9 p-3VB para -(CH2)3N(CH3)2 Acetonitriiee 0.11 11.8 m-ZVB meta -(CH2)2N(CH3)2 Benzene 0.15 16. m-2VB meta -(CH2)2N(CH3)2 Acetonitrilee 0.31 24. a0.01 - 0.10 M Ketone in degassed solutions at room temperature. bQuantum yield for acetophenone formation, extrapolated to infinite dilution. cDetermined by SV quenching with 1,3-pentadiene, extrapolated to infinite dilution. d0.40 M Pyridine added. “2% H20 added. 109 .mcmvumacwa-m.— sue: mucmemmnammvc ocoumx acvgucosc >5 emceeLmawv mapm> .mn «unmemwmm soc; mm=~m> y .PPP mucmemems son» mmape>m u .mcmvuoucmaim.— saw: mcwgozoaa >m x: necessmuoau .covumsgom mcocasaoumuo cow upm_a ssacazon .»m an Aomz “NV mppeuvcoumum am: so mcm~=mn vmmmmomu cw acoumx z no.0 . ~o.co .em.F eomo.o o..eeeeaeoo< Nfimzuvz- I- <-m aoe.o emmo.o oeoneom ~2m=evz- z- <-m e.m omo.o a__eoeeaeoo< «Amzevz- mzeo- mmoo:-a om.a omuo.o oeomeom Nfimzovz- mzuo- ”moo=-a aommom. .oe o_,eo_aaooo< mxu- Nflmzuvzmfimzuvo- m>m-a oo_nooom eo.o oeoaeom mzu- Nfimzuvzmfimzuvo- m>m-a oeax ea peo>_om . .a a 52a: a a.meoeam-ae_e< toe apao oeeoe_eoeoea .4. opaae 110 15.0 13.0 .1.1141 T. 1033"1 9.0 7.0 I I I I I l 0.04 0.08 0.1 2 [Ketone] .14 Figure 37. Extrapolation of Triplet Lifetimes of p2VBO and p3VB. in Acetonitrile. 111 6.0 +- o 5.0 - 4.0 +- IO T o 3.0 F o 2.0: F o C 1.0 2.0 4.0 5.0 8.0 100 [01,10’5111 Figure 38. Stern Volmer Plot for Diene Quenching of Room Tempera- ture PhoSphorescence of m-Carbomethoxybenzophenoneo and p-Carbanethoxybenzophenone. in CC14. 112 I k I I L 0.40 0.80 1.2 1.6 2.0 [01,10'4M Figure 39. Stern Volmer Plot for Diene Quenching of Room Tempera- ture Phosphorescence of p2BB in CC14. 113 from 1:1 solutions of carbomethoxybenzophenone and the model N,N- dimethylaminoethylbenzoate quencher were measured and compared to the emission from an equimolar amount of the amino-ketones in order to obtain an estimate of self-quenching by the amino-ketones. The results are summarized in Table 15. As a comparison, the rate of quenching of butyr0phenone by both 2,5-dimethylhexa-2,4-diene and triethylamine in carbon tetrachloride was measured (Figure 40). 2. Quantum Yields Quantum yields for acetophenone formation were determined by parallel irradiation at 313 nm of 0.01 - 0.10 M ketone solutions and 0.10 M valerophenone actinometer in a merry-go-round apparatus.13 All samples were adequately degassed prior to irradiation and con- version was usually kept below 10%. In most cases both the ketone solution and the actinometer absorbed all the incident irradiation; in those cases (low ketone concentration) where some of the light was transmitted, then suitable corrections were made. The values are included in Tables 12-14 and the extrapolation of quantum yields to infinite dilution for p-2VB and p-3VB and for m-2VB in aceto- nitrile are shown in Figures 41 and 42. 3. Dippppearance Qpantum Yields Disappearance quantum yields determined for p-2VB and p-2AB were extrapolated to infinite dilution (Figure 43) in order to determine whether the Norrish Type II photoelimination is the major 114 .gmumm pmuos op coconsou mo upo_z saacmsa cw mmmmeowu soc» cmpms_um0 o=Pe> u .xnoumogauoam zmmpe x; vmezmmme mE—umewp 03m: oo_ a museum; mm mucogmwmmu .4 a eaoaeeoma Fee a, .-a .-z a o_ x e.a xv nee—5-4 .AxupmoUmv> mu? sogw wiuxw:~>:umspuim.~ saw: mcwcucmac >5 umcpsgmumu mmspm> a .ogaaoemnsmu soon as mcopuzpom «poo ummmmmmc a? macaw; 2 etc, x o.p so» cmcwsemumo mmspm>o ee._a --- mo.o cue Nfimzovzmxumzu- apes mm~-e ~_.o a.~ .P ewe mzu- aeoe m.P mm.o mo.o oee NAmzuvzmzomze- aeaa mmN-a mo.o o~.m .2 see «:0. aeaa m o_ .e\~ op .ecx no o.o a cowupmoe use: _- m m Foe 25:3 2 .mococmcao~:om cmusapumaam go; mama mucmumogozamoga .mp mpnmh m 115 6.0 - 5.0 - O 4.0 - 0 (to 3.0 (- O 0 2.0 L O O 1.0 0' 2.0 . 4.0 . 6.0 [01,10'3M Figure 40. Stern Volmer Plot for 0.040 M Butyrophenone in CC14 with Hexadiene-Quen’chero or Triethyl amine Quencher.. 116 O O 14.0 ~ . a O 12.0 - . Q C .1. - 0n . D 10.0 " 3 8.0 - 0.04 0.08 0.12 [Ketone],M Figure 41. Extrapolation of on for p2VBO and p3VB. in Aceto- nitrile to Infinite Dilution. 117 13:1 - l I 1 1 l l 0.02 0.04 0.06 [Ketone] .M Figure 42. Extrapolation of 011 for m2VB in Acetonitrile to In- finite Dilution. 118 0.5 - O b o 0-x 0.3 t- . 0.1 - 1 L 1 J L 0 02 0.04 0.06 0.08 0.1 0 [Ketone] ,M Figure 43. Extrapolation of A-K for p2VBO and p2AB. in Aceto- nitrile to Infinite Dilution. 119 source of ketone disappearance or if charge transfer processes (both intramolecular and intermolecular) efficiently lead to product forma- tion. The errors involved are fairly large, but accurate enough for this purpose. The ketones were usually photolyzed to greater than 20% conversion. DISCUSSION A. Bifunctional Molecules The study of bifunctional molecules enables one to limit the number of conformations in which the donor and acceptor orbitals overlap. In order to investigate the effect of triplet state electronic configuration on CT quenching, the following system was chosen for study, since both m-ZVB and p-ZBB have n,n* lowest 23 I - n-C4H9 (Z-VB) :0 ll Ph (2-BB) triplets, while p-2VB has a n,n* lowest triplet. Identical confor- mational restraints are present in both p-2VB and p-ZBB. Another interesting system includes the following amino-ethers OMe, R' = NMe2(p-MeO3E) - 0(CH2)3NMe2, R'=CH p-3VB) ‘0 I :0 :0 1 11 3( in which the only significant difference involves the different ap- proach of the donor to the acceptor orbital. Both compounds possess identical energetic parameters, including a h,n* lowest triplet. The following kinetic expression holds for these bifunctional 120 121 1/1 = kr + kd + k k ~ [Ketone] (16) 01 intra + 01 inter molecules since the triplet lifetime, 1, is dependent on the rate constant for hydrogen abstraction, kr’ the rate constant for radia- tionless decay, kd, the rate constant for intramolecular charge transfer quenching, kCT intra’ and the bimolecular rate constant for charge transfer quenching, kCT inter' The sum of kd and kr can be obtained from the triplet lifetimes of the model carbomethoxy ke- tones and estimates for aminoiketone self-quenching rates can be obtained by quenching the carbomethoxy models with suitable tertiary amines. Extrapolation of triplet lifetimes to infinite dilution eliminates any intermolecular CT quenching by the amino-ketone and simplifies the kinetic expression. l/r“ = kr + kd + kCT intra (17) Thus, the rates of intramolecular CT quenching in bifunctional molecules can readily be determined. 8. Amino-Esters Winnik et_gl,84’85 have studied the intramolecular CT quenching of benzophenone emission by alkenes in the following system ° CHzlnCH=CH2 122 and observed no intramolecular charge transfer quenching when n < 9. For short methylene chains the double bond can come into contact with the phenyl ring, but cannot approach the carbonyl moiety. Thus, the lack of CT quenching in these compounds suggests that the electron-deficiency in the n,n* excited benzophenone must be located on the carbonyl n-orbital. 64a the Since tertiary amines are better donors than alkenes, analogously substituted benzophenones would provide better evidence for the localization of excitation energy on the carbonyl in n,n* triplets. Table 15 contains the phosphorescence data in carbon © © 0(cH212NM02 tetrachloride for p-ZBB and m-ZBB, as well as the data for the model p- and m-carbomethoxybenzophenones. The triplet lifetimes were measured by diene quenching of phosphorescence emission. p-ZBB has a shorter triplet lifetime than the model p-carbomethoxybenzo- phenone (ID = 8 usec and 130 usec, respectively) and the decrease in lifetime is paralleled by a decrease in emission intensity. The triplet lifetime of m-carbomethoxybenzophenone measured was 0.6 usec and the triplet lifetime of m-ZBB, as determined by com- parison of emission intensities of equimolar solutions of m-2BB and model ester, is 0.05 usec. The rates of intermolecular CT 123 quenching in carbon tetrachloride were determined by comparing the emission of the model compounds containing equimolar amounts of y-dimethylaminoethyl benzoate with the emission from equimolar amounts of p-ZBB or m-ZBB. The values for bimolecular CT quench- 1 1 ing for the para- and meta-amino-ketones are 3 x 107 M' s- and 2 x 108 1 1, respectively. These values are somewhat lower than the M' 5' value one would predict on the basis that triethylamine quenches triplet butyrophenone at a slightly faster rate in carbon tetra- chloride (l.6 x 109 M'ls'1) than in benzene (1.2 x 109 "-15-1). In any case, the rate of intramolecular CT quenching is 04 x 105 s‘1 which is 102-103 times slower than the rate for intermolecular CT quenching in carbon tetrachloride. Thus, the low rates of intramolecular CT quenching by the amine moiety in these short chain compounds support Winnik's results with the alkenyl moiety,84’85 suggesting that the excitation of the benzophenone n,n* triplet is localized on the carbonyl moiety. Unfortunately, since the aminobenzophenones react with trace impurities in the carbon tetrachloride or with the solvent itself to form quaternary ammonium salts (isolated and identified by NMR) upon standing, it was necessary to establish the amount of free amine in solution when the experiments were conducted. A FT-250 MHz NMR of 1.0 x 10'4 M p-ZBB in carbon tetrachloride pulsed for 4 hours showed only a 15% decrease in free amine as compared to a tetrachloroethane standard. This result would imply no more than a 30% decrease in free amine over a 4 to 4-1/2 hour period, since a time-average value was obtained. Thus, within the time 124 frame of these experiments, only a small percentage of the free amine became protonated. Also, the quaternary alimonium salt was not sufficiently soluble in the carbon tetrachloride solution to be detected in the NMR spectrum and a blank of the HCl salt of p-ZBB in carbon tetrachloride showed no appreciable room temperature phos- phorescence. The lifetime of the quarternary salt would be expected to be similar to the carbomethoxybenzophenone models, since the lone pair on the nitrogen atom is no longer available for CT quenching interactions. Thus, it was concluded that the observed phosphor- escence emission was indeed from the free amine. Other solvents such as acetonitrile, benzene, heptane, methylene chloride, t-butyl alcohol, distilled water, and chlorobenzene also had been tried, but solvent emission prevented detection of ketone phosphorescence. Further studies to determine the triplet lifetimes of the amino- benzophenones in acetonitrile will be undertaken in this group. Table 17 contains the Type II quantum yields, triplet lifetimes extrapolated to infinite dilution, and the rate constants for y- hydrogen abstraction and intramolecular CT quenching for the amino- esters p-2VB, m-2VB, and p-3VB. Both p-ZVB and p-3VB show rapid = 5.1 x 108 1 and 6.6 x 108 intramolecular CT quenching (kCT intra s' 1 s' , respectively, in acetonitrile), while m-2VB shows negligible intramolecular CT quenching. Also, p-2VB undergoes rapid intra- 8 5") in benzene, molecular CT quenching (kCT intra = 3.8 x 10 while the meta isomer does not. The low quantum yields for the para amino-ketones reflect the intramolecular CT quenching, but the reason for the low quantum yield for m-2VB is not fully understood. 125 Table 16. Charge Transfer Quenching Data for Valerophenone Models.a WI b CT inter’ 7 -1 8 -1 -1 R Solvent kH,lO s 10 M as p-coch3 Benzene 12. 38.“ p-COZCH3 Benzene 12. 31.e p-c020H3 Acetonitrile 17. 69.“ p-0020H3 Acetonitrile 17. 81.e m-COZCH3 Benzene 28. --- m-c020H3 Acetonitrile 48. 38.“ p-OCH3 Benzene 0.12 0.6f p-00H3 Acetonitrile 0.16 3.29 a0.040 M Ketone in degassed benzene or wet acetonitrile (2% H20) solution. bDetermined by sv quenching with 1,3-pentadiene. cDetermined by SV quenching with various tertiary amines. dB-Dimethylaminoethyl benzoate quencher. 'ev-Dimethylaminopropyl benzoate quencher. fEstimated from solvent effects on quenching of p-methoxyvalero- phenone with triethylamine obtained by Warren 8. Mueller. gN,N-Dimethylaminopropyl phenyl ether quencher. 126 Long alkyl chains are known to lessen the efficiency of product formation from the intermediate biradicals112 and could partially explain the lower quantum yields. From the kinetic and spectros- copic studies presented in Part I, it was concluded that p-carbo- methoxyvalerophenone has nearly isoenergetic triplet states. Assum- ing a Boltzmann population, the n,n* and n,n* triplets are nearly equally populated in p-carbomethoxyvalerophenone, and analogously, in p-ZVB. Thus, one would estimate the rate for intramolecular CT quenching of the n,n* triplet in these amino-esters aS‘MI x 109 s'1 in acetonitrile. Since both carbomethoxyvalerophenones and carbomethoxybenzo- phenones have similar excited state reduction potentials (Table 19), these results seem to support the idea that excitation of the n,n* triplet is localized primarily on the carbonyl, while excitation of the n,n* triplet lies primarily on the benzene ring (Scheme 5). 1r,1r triplet Scheme 5. Valence Bond Representations of p-ZBB and p-2VB. 127 -4.2 :42: 442454444 >4 44 eoe2ELoeo4w 42422 2:244:44 .24 44 445224244 24 .co2ps22u mu2c2m=2 on noun—cameuxm .mcm2ueucmn .co2ua22u ma2c2ec2 on umu42oameuxm .covumsgom ococogaoumue com 1 any ~222u2=ou504 no: go mco~coa 43444444 :2 mcouox.z o2.o-2o.o4 --- 4.4 4.4 44.4 422:22452454 4244422424442- oboe 4>4-e -- 4.4 2.4 42.4 5:44:54 4244422424442- aooe 4>4-e --- 4.4 4.4 44.4 422222454554 444- 4455 --- 4.4 4.4 44.4 4:44:54 4:4- 4245 4.4 2.2 4.4 22.4 422:22eaeooe 4244422424442- 4:44 424-4 2.4 2.2 2.4 42.4 422222442454 4244422424442- 4:44 4>4-a 4.4 4.2 4.4 24.4 oeoNeo4 4244422424442- aeaa 4>4-a --- 2.2 2.2 44.4 422242442554 4:4- 4:44 --- 4.2 4.2 42.4 4:44:44 4:4- 4:44 2-4 442 2-4 442 52-4 442 224 244.254 4 44222454 oeaz .42442 244 .44 .e\2 a .mempmm-o:25< see 4449 mc2gocoao memcae» mmgegu .42 42444 a 128 Since the para-valeryl amines undergo rapid internal and external CT quenching, it was necessary to determine whether CT quenching leads to product formation. The disappearance quantum yields for p-ZVB and p-ZAB (the acetophenone analogue) were measured and extrapolated to infinite dilution (Figure 42). At 0.040 M ketone Q-K = 0.39 and 0.43 for p-ZVB and p-ZAB, respectively. while at in- finite dilution. °~K = 0.28 and 0.02, respectively. Since 011 = 0.l3 for p-ZVB at infinite dilution and relatively large errors are involved in the measurement of disappearance quantum yields, then one can assume that intramolecular CT quenching leads to little, if any. nonvolatile photoproduct formation. This result is expected since the hydrogens a to the nitrogen are unavailable for intra- molecular abstraction by the radical anion. , GS. Thus, intermolecular CT interactions must lead to photoreduction 60 products by a-hydrogen abstraction and subsequent radical-coupling to give nonvolatile photoproducts. C. Amino-Ethers In order to determine the generality of these results, the following amino-ethers were investigated and the results are 129 O R= OCHB, R'=N(CH3)2(p-MeO3E) presented in Table l4. In both acetonitrile and benzene solvents, p-Me03E undergoes rapid intramolecular CT quenching (kCT intra = 2.8 :< 109 s'1 and 5.4 x 108 s'], respectively) as compared to inter- molecular CT quenching rates of 3 x l08 and 6 x l07 in acetonitrile and benzene. Conversely, p-3VE undergoes CT quenching with a rate constant of 6 x 107 s"1 in acetonitrile and only 5.] x l04 s"1 in benzene, compared to rate constants for intermolecular CT quen- ching of 3 x 103 s“ and 5 x 107 s", respectively. The major dif- ferences between the two compounds involves the approach of the donor electron pair to the acceptor orbital, and the charge separa- tion involved in the excited state. One would expect a polar solvent such as acetonitrile to stabilize these charge separated forms. In the case of p-MeO3E, such charge separation would not be expected to significantly increase the rate of intramolecular CT quenching, since the nitrogen lone pair does not have access to the positively-polarized portion of the phenyl 130 .m4 wocmgmmmm Eng» 4444» mmzp4>m .444 44:444444 see» 4444» 443—4> .4444444444- um. 2 :44: muc4g4m444444 mcoumx mcvnucmsa 44 4444544444 4:24>4 .444442 co mucwspgmaxm 4:440:43: 44 4444544444 omx 44:4 covu4eucmucou 444444 5444 4444234444 4:24> m 4 .4444444444-4.4 :44: mcpgucmzc >4 44 4444544444 44=F4>u .copu4egom meocmsaoumU4 com 4444» 5444440“ .44 44 copuzpom 404: 444 :o_u=_o4 4444444444U4 no: go 4:44:44 44444444 44 mcoumx z mo. o-No. o4 .4444 .442 4.4444 4444.4 424444444444 4444442- 4- 4-4 .88 .22 W88 %84 2354 416;- 4- <4 .4444 4.4 4.2 .4444 444.4 424444444444 4444444- 4444- 44442-4 .444 4.44 4.2 4.444 4444.4 4444444 4444442- 4444- 44442-4 .44 4.4 4.2 4.44 .4e 424444444444 444- 44444424444444- 444-4 24.4v 4.2;. 4.2 4.2 44.4 4444444 444- 44444424444444- 444-4 ---- -- 4.2 4.2 24.4 424444444444 444- 4444- ---- -- 4.2 4.2 22.4 4:44:44 444- 4:44- 442 442 442 42-4 442 4444 4e4>2e4 .4 4 4442 ..Fox .hux .14— 4.4.). GLPCF L3:_. 0 . mLQEHmIO—bwflz LCM. mHflG a: P802030 80% mcmsh Umhmnu .mp mpnmh 13] ring. Thus, one would expect the normal polar solvent effects on the rate of intramolecular charge transfer quenching, as indicated by bimolecular CT quenching of p-methoxyvalerophenone (Table 16). Both the intermolecular CT quenching of p-methoxyvalerophenone and the intramolecular CT quenching of p-Me03E show a 5-fold increase in acetonitrile as compared to benzene. 0n the other hand, the nitrogen lone pair in p-3VE can come into contact with the electron- deficient portion of the phenyl ring, and one would predict rapid intramolecular CT quenching in acetonitrile. A 103-fold increase in intramolecular CT quenching for p-3VE was observed in acetonitrile as compared to benzene. 0. Summary of Charge Transfer_9uenching¥Results Table l9 summarizes the rate constants for CT quenching of amino-ketones. Since tertiary amines have oxidation potentials of 113 these CT interactions are either approximately 34 kcal/mole slightly endothermic or thermoneutral. The rapid intramolecular CT quenching of both y-dimethylaminobutyrophenone (3-A)73 and p-Me03E111 demonstrates the ready access of the amine lone pair to the electron "hole" in the n,n* and n,n* triplets, respectively. The slower rate of intramolecular CT quenching in p-3VE as compared to p-Me03E- in benzene is hard to explain, except on conformational factors, while the large increase in the intramolecular CT quenching rate of. p-3VE in acetonitrile as compared to benzene is probably due to charge separation in the excited n,n* triplet state. Charge transfer quench- ing is thermodynamically favorable for the amino-esters and both 132 4 442 x 4 4 442 x 4 444.444 4.44 4e.e n mop x 4 4 442 x 4 4 442 x 4 4 442 444.444 2.24 44.4 n mop x m a map x m 5.; no— x m 4 mo— x m mam.mmv ~.—~ a: = Eo—UQOFXN HQFGCF KN 4.4 442 x 2 4.4 442 x 4 444.444 4.44 44.4 4wwm44uz o 4-4 nmogm- ”whuhmw 444442 4 box mews? .hux .4442444 mcpgucmac 4444:44» omg4zu mo >u4es=m "mp mpn4h 133 mmNuE x WOF A X moP x —.V $¢oGN *2}: x New A x mop x —v $~.Nm k: c 4 me. x M). 4 co. v 444.4mv m.m~ *4 4 H mo— x w H mop x n on.¢mv m.Nm *=.= -m -z -m uogw- um_4_44 «444m4 up — uF a; «$33 4ma4_ .494 44444 .494 .4m44.ucou .m_ «.444 134 .ppp mocmgmmmm sag» :mxmu mwzpo>e .u:m>_om Focmcpozp .u:m>pom uvvgopzu -mgumu congoux .Aomz “NV ucm>pom mpvguwcoumu_ .u:m>_om ocm~cmm .Nm mucmsmmmm scum cmxmu wapm>m .Aawumpmg mozpm> pp< .mcocmzao~cmn gem Apmux ~.~¢v >m mw.p- ow umgmnsou A¢.¢mv >m p~._- u mmmzuuouus Lou van Apmox m.~mv >w om.p- u gmmzumou-a 40$ m_m4u:muoa cowuuauma$ .mumpm umpawgu vacuum 40$ my mwmmgacugma :4 mapm>m .mwcpsm agapugmu pmuoa mum44aogana gupz mpmuoe yo mcwzucoaa Loepo> cgmum sag; uocwsgmumc mmapm>u .mcmwvmpcmaum._ gu_z m:_;u:o=c gospo> :Lmam 504w umpapzopmu mmzpm>u .Awpos\_muxv hmuvmgm- u *umgm- corumacm msu sag; umumpaupmu macaw umpawsu ammzop mo pmwucwuoa cowuuaumg macaw cappuxu .mpmuoe co mapsmog upumcvxouosq ucu u_aoumosuumam Eog$ uocmwmma uopawgu ammzop $o mgaumzm ; pm, zmum Pam mOF x _. mm.fi_. it}... Ni _ o v F-mpuz u pun wwwmwmw mcoumx gou=_ .hux snug? .pox .4m44444oo .mp o_444 135 p-ZVB and p-3VB show appreciable intramolecular CT quenching, pre- sumably of the n,n* triplet, in both benzene and acetonitrile (k 8 m 5 x 10 5"), while m-ZVB (n,n* lowest triplet) shows CT intra very little if any intramolecular CT quenching (kcT intra :106 5"). Since the benzophenone esters have excited state reduction potentials comparable to those of their valeryl analogues and undergo only slow 5 5'1), one can conclude that intramolecular CT quenching (kCT 5.1 x 10 the n,n* excitation is localized primarily on the carbonyl. The naphthyl analogue of 3-A (B-3N)82 shows only slow intramolecular CT quenching in methanol, presumably since the CT interaction is highly endothermic. Thus, although some trends in CT quenching of bifunc- tional molecules are evident, further research is necessary in order to understand better the conformational factors involved and the differences in CT quenching of n,n* and n,n* triplet states. E. Suggestions for Further Research l. The methylene chains on both the amino-esters and the amino- ethers could be extended in order to determine the conformational effects on electron donor and acceptor orbital-overlap on CT quench- ing rates. 53 (”.2 . x OorC=O X. ’ . R n-C H 49°” 136 2. The effects of other electron donors, such as other hetero- atoms or alkenes, on intramolecular CT quenching could be studied. R = n-C4H9 or ¢ 3. Intramolecular CT interactions in 3-benzoylpropionate esters could be investigated, since both the nature of the lowest triplet and the excited state reduction potential of the ketone can be varied without affecting the orbital overlap between donor and acceptor moieties. >< ll H9 CF39 CN’ Etc. ..< I - N(CH3)2 or CH=CH¢ 4. Solvent effects on intramolecular CT quenching rates in bi- functional molecules could provide interesting results, especially in molecules where charge separation can occur in the excited state. 86 5. Since Mashuhara's conclusions about internal hydrogen ab- straction seem questionable, the following system could be studied. 137 / M‘2"‘."‘cl-I:z) . " ‘ 1'2-3 The rate of intramolecular CT quenching can be determined by quench- ing Type II photoproduct formation and the results compared with those of Mashuhara. EXPERIMENTAL A. Preparation and Purification of Chemicals l. Solvents and Additives figflggng, One gallon of thiophene-free Mallinckrodt reagent grade benzene was stirred repeatedly over 200 ml portions of con- centrated sulfuric acid for 1 day periods until the sulfuric acid no longer discolored. The benzene was washed three times with distilled water, 4-5 times with saturated sodium bicarbonate solu- tion (until a white precipitate no longer fOrmed in the aqueous layer), then 4 times with distilled water, and dried over magnesium sulfate. Phosphorous pentoxide (loo 9) was added and the benzene was refluxed overnight and distilled through a one-meter column packed with stain- less steel helices at a rate of 100 ml/hr. The first and last l0-l5% portions of the benzene were discarded. Acetonitrile (Mallinckrodt spectrophotometric or MCB OmniSolv) was used as received. Carbon Tetrachloride (Fisher Scientific Company - spectranalyzed) was purified following the procedure of Schuster.114 Carbon tetra- chloride (1 liter) containing 0.1 g benzophenone was photolyzed for 2 hours under an inert atmosphere (solution turned yellow). The 138 139 solvent was refluxed for 4 hours and distilled through a 60 cm column packed with glass helices at a rate of 100 ml/hr. The first and last 200 ml portions were discarded. Methanol. Mallinckrodt reagent grade methanol (1 liter) was purified by distillation from magnesium turnings (lg) through a 60 cm column packed with glass helices. The middle fraction («60%) was collected, bp 64-65°. Pyridine (Fisher Scientific Company reagent grade) was distilled from barium oxide through a 60 cm column packed with glass helices, and the middle fraction («J0%) was collected and redistilled, bp ll4.5-llS°. Dioxane. MCB Scintillation grade dioxane (500 ml) was refluxed for 3 hours through a 50 cm column packed with stainless steel helices, followed by distillation (50 ml/hr). The first and last lOO ml portions were discarded. tert-Butyl Alcohol. Fisher Scientific Company tert-butyl alcohol (500 ml) was distilled from magnesium turnings (l 9) through a 60 cm glass helice packed column at a rate of 50 ml/hr. The mid- dle 60% portion was collected. 115 Ethanol was purified according to Riddich's Technique by Dr. Harlan N. Frerking, Jr. One gallon of U.S.P. grade l90 proof 140 ethanol was distilled from 100 ml of concentrated sulfuric acid through a one meter glass helice packed column at a rate of 40 ml/hr. The middle 70% portion was collected and distilled from 60 g of potassium hydroxide and 30 g of silver nitrate. The middle 80% portion was collected and 200 ml of distilled water was added. The ethanol was redistilled and the middle 80% portion was collected. EPA Mixed Solvent. MCB Phosphorimetric grade EPA mixed solvent (5:5:2 ethyl ether, isopentane and ethyl alcohol) was used as re- ceived. 2-Methylbutane (Aldrich gold label spectrophotometric grade) was used as received. Methylcyclohexane (MCB reagent grade) was purified using Forster's technique."6 Methylcyclohexane (500 ml) was stirred over concentrated sulfuric acid until the acid no longer discolored. It was then washed with three 20 ml portions of distilled water, three 200 ml portions of saturated sodium bicarbonate, and then three 200 ml portions of distilled water. The methylcyclohexane was dried over magnesium sulfate and distilled through a 50 cm column packed with stainless steel helices. The first and last 100 ml portions were discarded. Toluene (Mallinckrodt) was purified in the same manner as benzene. In order to prevent sulfonation of the ring, the toluene was cooled 141 in an ice bath while being washed for only 2-3 hour periods with sulfuric acid. The middle fraction was collected, bp 110°. p-Xylene (Mallinckrodt reagent grade) was purified in the same manner as toluene. 2. Internal Standards Igigggggg (Aldrich Chemical Company) was purified by washing with sulfuric acid, followed by distillation, bp l05° (10 Torr) by Dr. Peter J. Wagner. Hexadecane (Aldrich Chemical Company) was purified by washing with sulfuric acid, followed by distillation, bp 146° (10 Torr) by Dr. Peter J. Wagner. Heptadecane (Chemical Samples Company) was purified by washing with sulfuric acid, followed by distillation, bp l58° (8 Torr) by Dr. Peter J. Wagner. Nonadecane (Chemical Samples Company) was purified'by recrystal- lization from ethanol. Eicosane (Eastman) was purified by recrystallization from ethanol. Heneicosane (Chemical Samples Company) was purified by re- crystallization from ethanol. 142 Docosane (Aldrich) was purified by recrystallization from ethanol. Tetracosane (Aldrich) was used as received. Hexacosane (Pfaltz and Bauer) was used as received. n-Octadegyl benzoate was prepared by esterification of benzoyl chloride (Matheson, Coleman and Bell) with n-octadecanol (Aldrich), mp 57-58°.. 3. Quenchers 1,3-Pentadiene (Chemical Samples Company) was used as received. cis 1,3-Pentadiene (Chemical Samples Company) was used as received. 2,5-Dimethylhexa-Z,4-diene (Chemical Samples Company) was allowed to sublime in the refrigerator. Triethylamnne (Matheson, Coleman and Bell) was stirred over potassium hydroxide (20 g) for 5 hours, then decanted off and distilled through a 60 cm glass helice packed column. The middle 60% portion was collected. 143 Naphthalene (Matheson, Coleman and Bell) was recrystallized from ethanol. B-Dimethylaminoethyl Benzgate was synthesized in the manner described fbr the analogously substituted ketones. Benzoyl chloride (14.1 g, 0.1 mole) in ether was reacted with excess N,N-dimethyl- ethanolamine (Aldrich) and subsequent workup gave the HCl salt of the desired product in 70% yield, mp l44-146°. Freeing the amine with aqueous base gave a colorless liquid. IR (neat) 1725 cm']; ‘H NMR (coc13) 2.25 (s, 6H), 2.6 (t, 2H), 4.3 (t, 2H), 7.1-7.5 (m, 3H), 7.8-8.1 (m, 2H); MS m/e 193, 71, 58. v-Dimethylamingpropyl Benzoate was prepared in a similar manner to its 2-carbon analogue. The HCl salt is a white solid, mp 156- 159.5°. The free amine is a colorless liquid. IR (neat) 1720 cm": ‘H NMR (coc13) 1.6-2.2 (m, 2H), 2.2-2.6 (m, 2H), 2.2 (s, 6H), 4.3 (t, 2H), 7.1-7.45 (m, 3H), 7.8-8.1 (m, 2H). N,N-Dimethylaminopropyl Phenyl Ether was prepared in a similar manner as the analogously substituted ketone. Phenol (9.4 g, 0.1 mole), N,N-dimethylaminopropyl chloride (13.59, 0.11 mole) and potas- sium carbonate (13.8 g, 0.1 mole) in 100 ml dry acetone were re- fluxed for 20 hours and subsequent workup gave the HCl salt of the desired product as a white solid (mp l44-l46°) after recrystalliza- tion from MEK/hexane. The free amine is a colorless liquid. IR (neat) 1595 cm"; ‘H NMR (coc13) 61.58-2.55 (m, 4H0),2.2 (s, 6H), 3.90 (t, 2H), 6.5-7.4 (m, 5H); MS m/e 179, 58. 144 4. Ketones valerophenone was prepared by the Friedel-Crafts acylation of benzene with valeryl chloride. Normal work-up procedures gave the crude product and distillation gave a colorless liquid, bp 105° (2 Torr). o-, m-, andgp-Trifluoromethylvalerophenones were available from a previous study.28 p-Hethoxyvalerophenone was available from a previous study.28 Substituted Valerophenones fbr which only reduction potentials or triplet energies were measured were available from previous studies.28’H7 Butyrophenone was available from a previous study.28 p-Methoxy-y-dimethylaminobutyrophenone was available from a previous study.82 Para-Fluorovalerophenone was prepared by Friedel-Crafts acyla- tion of Aldrich fluorobenzene with valeryl chloride. It was purified by vacuum distillation, bp 95° (0.16 Torr), mp 26°; IR (neat) l691 cm“; ‘H NMR (coc13) 50.9 (t, 3H), 1.1-2.1 (m, 4H), 2.89 (t, 2H), 6.8-7.2 (m, 2H), 7.7-8.0 (m, 2H); MS m/e 180, 138, 123. 145 Para-Cyanovalerophenone. Sodium cyanide (20 g, 0.41 mole) was partially dissolved by heating in 300 ml of DMSO; pgrg-fluorovalero- phenone (65 g, 0.36 mole) was added slowly to the mixture. The solution was heated to 110-130° for 5 hours, the reaction being fol- lowed by NMR monitoring of the aromatic region. The viscous brown mixture was poured into 600 ml water and extracted several times with ether. The combined ether extracts were washed first with water, then with saturated sodium bicarbonate solution, and were dried over sodium sulfate. The solvent was removed under vacuum and a brown oil (58 g, 0.31 mole) was isolated in 87% yield. NMR Analysis of crude product showed ~75% conversion. Vacuum distilla- tion provided 50 g (0.27 mole) of p-cyanovalerophenone as an oil bp 114° (0.1 Torr). Recrystallization from hexane gave white crystals, mp 34-35° (lit. 3.2-33)."8 IR (KBr) 1696, 2225 cm“; ‘H NMR (CDC13) 60.7-l.l (m, 3H), 1.1-2.0 (m, 4H), 2.85 (t, 2H), 7.78 (q, 4H); MS m/e 187, 145, 130. p-Fluorobutyrophenone was prepared by Friedel-Crafts acylation of Aldrich fluorobenzene with butyryl chloride and AlCl3 catalyst. After acidic workup, the desired product was isolated as a light yellow oil in 70% yield. IR (neat) 1690 cm"; 1H NMR (coc15)ao.5 (t, 3H), 1.5-2.1 (m, 2H), 2.87 (t, 2H), 6.8-7.2 (m, 2H), 7.6-8.0 (m, 2H); MS m/e 166, 138, 123, 95, 75. Para-Cyanobutyrgphenone was prepared, as described for p- cyanovalerophenone, in 70% crude yield. Vacuum distillation and 146 recrystallization from hexane gave a white solid, mp 43.5-45°; IR (KBr) 1690, 2220 cm“; ‘H NMR (c0c13) 60.8-l.2 (m, 3H), 1.5-2.0 (m, 2H), 2.91 (t, 2H), 7.74 (q, 4H); MS m/e 173, 145, 130, 102, 75. Para-fluoro-y-methylvalerophenone was synthesized by Freidel- Crafts acylation of Aldrich fluorobenzene with y-methylvaleryl chloride. IR (neat) 1670 cm"; ‘H NMR (CDC13) 60.6-l.l (d, 6H), 1.2-2.0 (m, 4H), 2.8 (t, 2H), 6.7-7.2 (m, 2H), 7.6-8.0 (m, 2H); M8 m/e 194, 138, 123. Para-Cyano-y-methylvalerophenone was prepared, as described for p-cyanovalerophenone, as a colorless liquid, bp 108° (0.8 Torr). IR (neat) 1690, 2225 cm"; ‘H NMR (CDC13) 60.91 (d, 6H), 1.4-1.8 (m, 3H), 2.90 (t, 2H), 7.80 (q, 4H); MS m/e 201, 145, 130. Meta-Cyanovalerophenone. n-Butylmagnesium bromide was prepared by adding 1-bromobutane (28 g, 0.2 mole) in 200 ml ether to Mg turnings (4.9 g, 0.2 mole) covered with ether. Aldrich m-cyano- benzaldehyde (26 g, 0.2 mole) was partially dissolved in 200 ml benzene, and the Grignard reagent was added dropwise with stirring. After being refluxed for 2 hours and then cooled, the solution was poured over dilute H2504/ice mixture. Normal work up gave l-(3- cyanophenyl)-l-pentanol as a light yellow oil (32 g, 0.17 mole). A solution of the crude alcohol (30 g, 0.16 mole) in 85 ml benzene was added slowly to a cooled mixture of 20 g (0.07 mole) sodium dichromate, 10 ml glacial acetic acid, 30 ml conc. sulfuric acid, 147 and 85 ml water.”9 After the solution was stirred at room tempera- ture for three hours, the layers were separated and the aqueous layer was extracted with benzene. The combined organic layers were washed first with 5% KOH solution and then water, then were dried over sodium sulfate. The oily solid (22 g, 0.12 mole) resulting from solvent removal was recrystallized several times from hexane to give white crystals, mp 52-53°. IR (KBr) 1682, 2230, cm"; 1H NMR (CDC13) 60.7-1.1 (m, 3H), 1.1-2.0 (m, 4H), 2.94 (t, 2H), 7.2- 8.3 (m, 4H); MS m/e 187, 158, 145, 130. Para-Valerylbengoic Acid. A solution of p-cyanovalerophenone (20 g, 0.11 mole), 30% KOH (100 ml), and ethanol (20 ml) was refluxed overnight. Careful acidification of the warm solution with dilute HCl resulted in precipitation of p-valerylbenzoic acid. Suction filtration of the solid followed by drying in a dessicator gave a white solid (16 g, 0.085 mole), mp 155-157°. IR (KBr) 1679, 1693 cm“; ‘H NMR (CDC13) 60.7-1.1 (m, 3H), 1.1-2.0 (m, 4H), 2.94 (t, 2H), 8.00 (d) of d, 4H), 9.7 (broad s, 1H); MS m/e 206, 189, 164, 149. Meta-Valerylbenzoic Acid. Hydrolysis of m-cyanovalerophenone (15 g, 0.98 mole) with 100 ml 30% KOH/ethanol solution according to the above procedure resulted in precipitation of an oily solid. The solution was extracted with ether and the combined ether ex- tracts were washed with water and dried over sodium sulfate. Evaporation of solvent, followed by recrystallization of the crude 148 product from ethanol/water, gave white crystals (11 g, 0.053 mole), mp 115-118°. IR (KBr) 1688 cm"; ‘H NMR (CDC13) 60.7-l.l (m, 3H), 1.1-2.0 (m, 4H), 2.94 (t, 2H), 8.00 (Q: 4H), 10.7 (broad s, 1H); MS m/e 206, 189, 164, 149. Para-Carbomethoxyvalerophenone. p-Valerylbenzoic acid (10.3 g, 0.050 mole), sodium bicarbonate (17 g, 0.15 mole), and methyl iodide (22 g, 0.15 mole) in 100 m1 dry DMF were stirred at room temperature in the dark f0r 18 hours.120 The mixture was poured into 400 ml of saturated NaCl solution, and the solution was extracted with ether. The combined ether extracts were washed with water and dried over sodium sulfate. Evaporation of solvent and recrystal- lization of the crude product from hexane (charcoal) gave white crystals (9.4 g, 0.043 mole), mp 81-82° (lit 6m."9 IR (KBr) 1676, 1724 cm“; ‘H NMR (CDC13) 60.8-1.l (m, 3H), 1.1-2.0 (m, 4H), 2.91 (t, 2H), 3.88 (s, 3H), 7.91 (d of d, 4H), MS m/e 220, 189, 178. 163. Meta-Carbomethoxyvalerophenone. m-Valerylbenzoic acid (21 g, 0.10 mole), sodium bicarbonate (34 g, 0.4 mole) and methyl iodide I (44 g, 0.3 mole) in 100 m1 dry DMF were treated in a similar manner to the 22:; compound. After work-up, evaporation of the solvent gave an oil (18 g, 0.8 mole) which was purified by vacuum distil- lation (bp 182° at 10 Torr), followed by low temperature recrystal- lization from hexane. IR (neat) 1690, 1729 cm"; ‘H NMR (CDC13) 60.7-1.1 (m, 3H), 1.1-2.0 (m, 4H), 2.94 (t, 2H), 3.89 (s, 3H), 7.2-8.5 (m, 4H); MS m/e 220, 189, 178, 163. 149 Para-Divalerylbenzene was prepared by reaction of Aldrich terphthalonitrile with 4 equivalents of n-butylmagnesium bromide. Mg turnings (9.7 g) were covered with anhydrous ether and l-bromo- butane (73 ml, 0.47 mole) in 200 m1 ether was added dropwise with stirring. A slurry of terephthalonitrile (12.8 g, 0.10 mole) in benzene was added slowly. After being refluxed overnight (solu- tion turned orange), the mixture was poured into dilute HCl/ice solution and extracted with ether. A small amount of p-divaleryl- benzene precipitated out of the aqueous layer and was collected. The combined organic extracts were washed with water and dried over sodium sulfate. Removal of the solvent gave a yellow, oily solid (12.6 g, 0.05 mole). The crude product was chromatographed on an alumina column using various petroleum ether/ether mixtures and the resulting eluted solid was recrystallized from hexane to give white crystals in 30% overall yield, mp 96-97°. IR (KBr) 1676 cm“; ‘H NMR (CDC13) 60.7=l.2 (m, 6H), 1.2-2.0 (m, 8H), 2.95 (t, 4H), 7.90 (s, 4H); MS m/e 246, 204, 189, 162, 147. Meta-Divalerylbengene. Similar synthetic and purification methods were used as described above for the parg-compound. Aldrich isophthalonitrile (12.8 g, 0.10 mole) in benzene was added slowly to n-butylmagnesium bromide (0.4 mole). After work-up, 11 g of a yellow oil was obtained (45% yield). After elution through an alumina column and repeated recrystallizations from petroleum ether, white crystals were obtained, mp 25°. IR (KBr) 1682 cm'l; 1H NMR (CDC13) 60.7-1.l (m, 6H) 1.1-2.1 (m, 8H), 2.98 (t, 4H), 7.2-8.5 (m, 4H); MS m/e 246, 204, 189, 162, 147. 150 Para-Acetylvalerophenone. A solution of Aldrich p-acetylbenzo- nitrile (8.0 g, 0.055 mole), ethylene glycol (10 ml), and p-toluene- sulfonic acid (0.1 g) in 50 m1 benzene was refluxed in a Dean-Stark trap until no more water azeotroped off. The cooled solution was washed first with water then with saturated sodium bicarbonate, and was dried over sodium sulfate. Evaporation of solvent gave the ketal as a white solid (9.8 g, 0.052 mole), mp 68-70°; ‘H NMR (CDC13) 61.60 (s, 3H), 3.4-3.8 (m, 2H), 3.8-4.2 (m, 2H), 7.48 (s, 4H). Magnesium turnings (1.25 g, 0.052 mole) were covered with dry ether; 1-bromobutane (7.1 g, 0.052 mole) in 200 m1 ether was added dropwise to maintain reflux. A slurry of the ketal (9.0 g, 0.047 mole) in 200 m1 benzene was added slowly with stirring. After being refluxed for 6 hrs the solution was poured into HCl/ice mixture and extracted with ether. Evaporation of the ether gave only starting material (2.2 g, 0.012 mole). The desired product (white solid) precipitated out of the aqueous solution (3.2 g, 0.016 mole) and, after recrystallization from hexane, gave white crystals, mp 77-78°. IR (KBr) 1676 cm"; NMR (CDC13 60.7-1.1 (m, 3H), 1.1-2.0 (m, 4H), 2.94 (t, 2H), 7.90 (s, 4H); MS m/e 204, 189, 162, 147. Ortho-Bromovalerophenone. n-Butylmagnesium bromide was made by the addition of 1-bromobutane (16 g, 0.12 mole) in 200 ml ether to magnesium turnings (2.8 g 0.115 mole) in ether. A slurry of Aldrich o-bromobenzaldehyde (18.5 g, 0.10 mole) in benzene was added slowly with stirring. After being refluxed for 2 hours and cooled, the solution was hydrolyzed with dilute HCl/ice water. Normal workup 151 gave a yellow oil (20.5 g, 0.085 mole) in 85% yield, IR (neat) 3300 cm']. The crude 1-(2-bromophenyl)-pentan-1-ol (9.7 g, 0.004 mole) was oxidized using sodium dichromate (24 g, 0.008 mole), glacial acetic acid (17 m1), and conc. sulfuric acid (30 ml) in 100 ml water following the procedure of Bruce.35 The solution was stirred for 5 hours at room temperature and then extracted with ether. The ether extracts were washed with 5% KOH solution and water, then dried over sodium sulfate. Removal of solvent gave a yellow 011 (5.1 g, 0.02 mole); IR (neat) 1700 cm"; ‘H NMR (CDC13) 60.7- 1.1 (t, 3H), 1.1-2.0 (m, 4H) 2.82 (t, 2H), 6.9-7.5 (m. 4H). Ortho-Cyanoyalerophenone. A solution of g-bromovalerophenone (20 g, 0.08 mole) and CuCN (10.0 g, 0.16 mole) in 25 m1 pyridine was refluxed for 2 hours. The mixture was added to 75 ml water and extracted with ether. » The combined ether layers were washed with water and dried over sodium sulfate. Evaporation of solvent gave a brown oil (13 g, 0.07 mole). Vacuum distillation gave a color- less oil, bp 117° (8 Torr). From low temperature recrystallization in hexane, a white solid was obtained, mp'b25°. IR (KBr) 1690 cm"; ‘H NMR (C0C13) 60.8-1.1 (t, 38), 1.1-2.0 (m, 4H), 2.82 (t, 2H), 7.4-7.9 (m, 4H); MS m/e 187, 145, 130. Ortho-Carbomethoxyvalerophenone. .g-Valerylbenzoic acid was synthesized following a procedure for keto-acids developed by 121 De Benneville. 'n-Butyl magnesium bromide (0.5 mole) in ether was cooled in an ice bath, and oven-dried CdCl2 (46 g, 0.25 mole) 152 was added slowly to the mixture. The mixture was allowed to warm and was refluxed for 1.5 hours. Solid phthalic anhydride (37 g, 0.25 mole) was added slowly with stirring to the cooled (0°) solu- tion. After being refluxed for 2.5 hours, the solution was cooled and dilute H2804/ice water was added. The organic layer’was sepa- rated and combined with ether extracts of the aqueous layer. The product was extracted from the ether layer with 10% K2C03 solution, which was then filtered and acidified with dilute H2504. The keto- acid was then extracted into ether; solvent evaporation left a clear oil (36.5 g, 0.17 mole). The oil eventually solidified in the re- frigerator and was washed with cold hexane to give a white solid, mp 40-42°. The free acid exists mainly as its hydroxy-y-lactone isomer; IR (KBr) 1750, 3360 cm"; ‘H NMR (coc13) 60.6-1.0 (m, 3H), 1.1-1.6 (m, 4H), 2.2 (broad t, 2H), 6.0 (broad s, 1H), 7.2-7.9 (m, 4H); MS m/e 206, 189, 164, 149 (base). The crude o-valerylbenzoic acid (20 g, 0.097 mole) was esteri- fied according to the procedure previously described involving stirring in the dark overnight with methyl iodide (30 ml, 0.48 mole) and sodium bicarbonate (15 g, 0.17 mole) in DMF (100 ml). After .ether work-up, evaporation of the solvent gave an orange oil (17 g, 0.078 mole) in 80% yield. Three consecutive vacuum distillations of the crude product gave a colorless oil, bp 116° (0.4 Torr). IR (neat) 1713, 1735, cm"; ‘H NMR (CDC13) 60.7-1.1 (t, 3H), 1.1- 2.0 (m, 4H), 2.74 (t, 2H), 3.8 (s, 3H), 7.2-7.9 (m, 4H); MS m/e 220, 189, 178, 163. 146. 153 3-Benggylbengonitrile. Phenyl magnesium bromide (0.08 mole) in ether was added dropwise with stirring to Aldrich m-cyanobenz- aldehyde (9.0 g, 0.075 mole) in 250 ml benzene. The solution was refluxed for 1 hour, cooled, and then added to dilute HCl/ice water. After hydrolysis was complete, the layers were separated and the aqueous layer extracted with ether. Normal workup gave a light yellow oil (12 g, 0.057 mole) in 76% yield; IR (neat) 2210, 3450 cm"; ‘H NMR (coc13) 62.55 (broad s, 1H), 5.7 (d, 1H), 7.0-8.0 (m,'»9H). The crude alcohol was oxidized to 3-benzoylbenzonitrile without further purification by the method described previously for l-(3-cyanopheny1)-1-pentanol. After benzene work-up, an oily solid was obtained which, after recrystallization from hexane, gave 3.0 g (0.14 mole) of white crystals, mp 88-90°. IR (KBr) 1710, 2200 cm"; ‘H NMR (CDC13)67.1-8.l (m); MS m/e 207. 130, 105 (base). Methyl 2-Benzqy1benzoate. Aldrich 2-benzoy1benzoic acid (9.1 g, 0.040 mole) was esterified as previously described using CH3I (10 ml, 0.16 mole) and NaHC03 (5 g, 0.06 mole) in 100 m1 DMF. Upon normal work-up, a yellow oil was isolated which was recrystallized twice from hexane to give a white solid (6.2 g, 0.026 mole), mp 48-49.5° (1it. 52°).122 IR(KBr) 1670, 1720 cm"; ‘H NMR (CDC13) 63.52 (s, 3H), 7.1-8.0 (m, 9H); MS m/e 240, 209, 163, 105. Methyl 4-Benzqylbenzoate. Aldrich 4-benzoylbenzoic acid (4.0 g, 0.018 mole) was esterified by refluxing overnight in methanol (50 ml) containing sulfuric acid (1/2 m1). Most of the solvent was 154 removed under aspirator pressure and water was added. The solution was made basic with K2C03 and extracted with benzene. The combined benzene extract was washed with water and dried over sodium sulfate. Removal of solvent gave a white solid, which was recrystallized from hexane (3 g, 0.13 mole), mp 108-109°. IR (KBr) 1640, 1715 cm"; 1H NMR (CDCl 63.88 (s, H), 7.0-8.1 (m, 9H); MS m/e 240, 209, 163, 105. 3) Methyl 3-benzoylbenzoate. 3-Benzoylbenzonitri1e (1.4 9, 0.0068 mole) was hydrolyzed in 50 m1 of 30% alcoholic KOH according to the procedure described previously. After work-up, l g (0.004 mole) of 3-benzoylbenzoic acid (tan solid) was obtained, which was recrystal- lized from MEK/hexane to give a solid, mp 161-163° (1it. 161-2°).123 IR (KBr) 1650, 1685 cm“; ‘H NMR (CDC13)67.3-8.5 (m, 9H), 9.9 (broad s, 1H). The ester was synthesized from 3-benzoy1benzoic acid (0.5 g, 0.003 mole) by refluxing overnight in 50 m1 methanol containing a trace of sulfuric acid, the procedure previously described for the pgrg_analogue. After similar work-up and recrystallization from hexane, white crystals were obtained (~0.2 9), mp 43-45°. IR (KBr) 1650 1725 cm"; ‘H NMR (CDC13) 63.82 (s, 3H), 7.1-8.4 (m, 9H); MS m/e 240, 209, 163, 105. 3-Trifluormethylbenzophenone. Aldrich m-trifluoromethylbenzo- nitrile (4.3 g, 0.025 mole) in benzene was added dr0pwise to an ether solution containing 0.03 mole phenyl magnesium bromide; the 155 mixture was refluxed for 2 hours. Dilute HCl/ice water was added and the layers were separated. The organic layer contained mostly unreacted bromobenzene. The aqueous layer was heated on the steam bath for 2 hours, followed by cooling and extraction with ether. The combined ether extracts were washed with water and dried over sodium sulfate. Evaporation of the solvent gave crude product; recrystallization from hexane gave white crystals (1.4 g, 0.006 mole), mp 49-51°. IR (KBr) 1650 cm“; ‘11 101R (CDC13) 67.2-8.0 (111); MS m/e 250, 173, 145, 105 (base).77. p-Valeryl B-Dimethylaminoethyl Benzoate. p-Valerylbenzoic acid (10.0 g, 0.05 mole) and thionyl chloride (4 ml, 0.06 mole) in 50 ml benzene were refluxed under anhydrous conditions, followed by removal of excess thionyl chloride and partial removal of solvent under aspirator pressure. The solution was then cooled (0°) and 300 m1 anhydrous ether was added. Excess N,N-dimethylethanolamine (Aldrich) was added dropwise with stirring with the evolution of much HCl gas. The white solid (12 g) was filtered off, and NMR analysis revealed the HCl salt of the desired product with little starting alcohol. Addition of more N,N-dimethylethanolamine to the filtrate gave very little additional solid. More product could oc- casionally be obtained by bubbling HCl gas through the filtrate and filtering off the precipitate (mixture of starting alcohol and the desired product). The solid was dissolved in the minimum amount of distilled water (10-20 m1) and the solution was made basic (pH m9) by the addition of potassium carbonate (carbon dioxide was 1S6 evolved). The solution was extracted three times with benzene (20 ml) and the combined benzene solution was washed once with 5% KOH solution (to remove starting acid), fOur times with distilled water (to remove starting alcohol), and dried over sodium sulfate. Removal of solvent under vacuum gave a light yellow oil. The oil was dis- solved in anhydrous ether and HCl gas was bubbled through the solu- tion. The precipitated HCl salt of the amino ester (off-white solid) was filtered and washed with ether. Recrystallization of the HCl salt from MEK (charcoal) gave a white solid, mp l35-l37.5°. The HCl salt was dissolved in the minimum amount of water (5-10 m1) and the solution was made basic with potassium carbonate and ex- tracted with ether. The combined ether extracts were washed three times with distilled water and dried over sodium sulfate. Removal of solvent under vacuum gave a colorless oil. IR (neat) 1685, 1720 ‘H NMR (00c13) 60.7-1.1 (m, 3H), 1.1-2.0 (m, 4H), 2.30 (s, 6H), 2.64 (t, 2H), 2.92 (t, 2H), 4.36 (t, 2H), 7.92 (d of d, 4H); MS m/e 277, 248, 220, 189, 149, 104, 71, 58 (base). cm']; m-Valeryl fi-Dimethylaminoethyl Benzoate was prepared in a similar manner as the pg§g_isomer. ‘eralerylbenzoic acid (10.0 g, 0.05 mole) and thionyl chloride (4 ml, 0.06 mole) in 100 m1 benzene were refluxed for 4 hours, followed by removal of excess thionyl chloride and partial removal of solvent under aspirator pressure. The dropwise addition of excess N,N-dimethylethanolamine to the ether solution gave a yellow oil, and the solution was decanted off. Similar work-up gave the HCl salt as a light yellow oil. Attempted 157 low temperature recrystallization from hexane gave a “taffy-like" off-white semi-solid. The HCl salt was freed as described for the pgrg_isomer to give the desired amine and subsequent chromatography on a short alumina column using petroleum ether/ether mixtures gave a pale yellow liquid. IR (neat) 1685, 1720 cm"; 1H NMR (coc13) 60.7-l.l (m, 3H), l.l-2.0 (m, 4H), 2.33 (s, 6H), 2.68 (t, 2H), 2.95 (t, 2H), 4.38 (t, 2H), 7.4 (t, lH), 7.9-8.l (m, 2H), 8.4-8.53 (m, 1H); MS m/e 277, 220, 189, l49, l04, 71, 58 (base). p-Acetyl B-Dimethylaminoethyl Benzoate was prepared in a similar manner as the valeryl analogue. Aldrich pracetylbenzoic acid (2.0 g, 0.01 mole) and thionyl chloride (2 ml, 0.03 mole) were refluxed for 2 hours (solution turned brown), fOllowed by removal of unreacted thionyl chloride and partial removal of solvent under aspirator pres- sure. The dropwise addition of excess N,N-dimethylethanolamine to the ether solution gave a brown oil, and the solution was decanted off. Similar work-up and recrystallization from MEK/hexane gave a white solid (HCl salt), mp l68-l7l°. The HCl salt was freed in a similar manner to give a colorless liquid. IR (neat) l685, l720 cm"; ‘H NMR (coc13) 52.3 (s. 6H), 2.58 (s, 3H), 2.55 (t, 2H), 4.38 (t, 2H), 7.92 (d of d, 4H); MS m/e 235, 220, 147, 104, 71, 58 (base). p—Valeryl_8-Dimethylaminopropyl Benzoate was synthesized in a similar manner as the 2 carbon analogue. .ngalerylbenzoic acid (l0.0 g, 0.05 mole) and thionyl chloride (4 ml, 0.06 mole) were refluxed for 4 hours, followed by removal of solvent under aspirator 158 pressure. The dropwise addition of excess 3—(N,N-dimethylamino)- 1-pr0panol (Aldrich) to the ether solution (25°) gave an off-white solid (12.1 g) which was filtered. Similar work-up and recrystal- lization from MEK/hexane gave a white solid (HCl salt), mp 203-204°. The HCl salt was freed in a similar manner to give a colorless liquid. IR (neat) 1535, 1720 cm"; ‘H NMR (cnc13) ao.7-1.1 (m, 3H), 1.1-2.1 (m, 6H), 2.1-2.63 (m, 2H), 2.23 (s, 6H), 2.84 (t, 2H), 4.34 (t, 2H), 7.94 (d of d, 4H); MS m/e 291, 234, 147, 102, 86, 58 (base). p-BenzoylB-Dimgthylaminoethyl Benzoate was prepared in a similar manner as the valeryl analogue. Aldrich p-benzoylbenzoic acid (3.0 g, 0.013 mole) and thionyl chloride (1.2 ml, 0.18 mole) in 100 m1 ben- zene were refluxed for 5 hours. Ether was added and the dropwise addition of excess N,N-dimethylethanolamine (Aldrich) gave an oily white solid which was filtered and identified as N,N-dimethylethanol ammonium chloride. Additional starting alcohol was removed by bubbling HCl gas through the solution and filtering off the pre- cipitate. The solvent was then removed under vacuo to give a yellow oil and similar work-up gave the desired HCl salt as an off-white solid. Recrystallization of the HCl salt from MEK gave a white solid, mp 168-171°. The HCl salt was freed in a similar manner to give a white solid, mp 39.5-42°. IR (KBr) 1545, 1700 cm"; 1H NMR (coc13) 62.30 (s, 6H), 2.65 (t, 2H), 4.37 (t, 2H), 7.2-8.2 (m, 9H); MS m/e 297, 209, 105, 77, 71, 58 (base). 159 m-Benzoyl B-Dimethylaminoethyl Benzoate was synthesized in a similar manner as the parafisomer. 3-Benzqylbenzoic acid (1.0 g - synthesis previously described under methyl 3-benzoylbenzoate) and thionyl chloride (1 ml) were refluxed for 3 hours, followed by re- moval of excess thionyl chloride and partial removal of solvent under aspirator pressure. Similarly, the dropwise addition of excess N,N- dimethylethanolamine (Aldrich) gave an oily white solid which was filtered and identified as N,N-dimethylethanol ammonium chloride. Evaporation of solvent gave an off-white semi-solid and similar work- up and attempted recrystallization from hexane gave the HCl salt as a "taffy-like", off-white semi-solid. The HCl salt was freed in a similar manner to give an almost colorless liquid. IR (neat) 1660, 1720 cm“; ‘H NMR (coc13) 52.30 (s, 6H), 2.65 (t, 2H), 4.37 (t, 2H), 7.2-8.4 (m, 9H); MS m/e 297, 209, 105, 77, 71, 58 (base). p-(3-0imethylaminopr9poxy)valerophenone was synthesized follow- 124 ing the procedure developed by Allen and Gate for phenolic ethers. Eastman 4'-hydroxyvalerophenone (5.4 g, 0.030 mole), 3-dimethy1amino- propyl chloride 4.3 g, 0.035 mole (obtained by freeing Aldrich HCl salt with aqueous base and extracting with ether), and potassium carbonate (4.2 g, 0.030 mole) in 100 ml dry acetone were refluxed for 16 hours under anhydrous conditions. After solvent removal under vacuo, 100 ml distilled water was added and the solution was extracted 3 times with 75 m1 benzene. The combined organic extract was washed with 10% KOH, then 3 times with distilled water and dried over sodium sulfate. Removal of solvent gave an oil. The 160 oil was dissolved in ether and HCl gas was bubbled through the solution. The profuse amount of soap-like white precipitate was filtered and recrystallized from MEK/hexane to give white solid (HCl salt of the desired amine, mp 156.5-158°. The amine was freed by dissolving the HCl salt in the minimum amount of distilled water, making the solution basic (pH'M9) with potassium carbonate, and extracting with ether. The combined ether extract was washed with distilled water and dried over sodium sulfate. Evaporation of sol- vent gave a colorless liquid. IR (neat) 1600, 1675 cm"; ‘H NMR (00013) 60.7-l.1 (m, 3H), 1.1-2.6 (m, 8H), 2.2 (s, 6H), 2.86 (t, 2H), 4.0 (t, 2H), 7.2 (d, 2H), 7.8 (d, 2H); MS m/e 263, 120, 86, 58 (base). p-(3-Dimethylgminopropoxy)acetophenone was prepared in a similar manner as the valeryl analogue. Eastman 4'-hydroxyacetophenone (13.6 g, 0.10 mole), Aldrich 3-dimethylpropy1 chloride (13.4 g, 0.11 mole), and potassium carbonate (13.8 g, 0.10 mole) in 100 ml dry acetone were refluxed for 20 hours. Similar work-up procedures and re- crystallization of the HCl salt from MEK/hexane gave a white solid, mp 177-178°. The amine was freed in a similar manner to give a 1; ‘H NMR (coc13) 61.68- 2.75 (m, 4H), 2.2 (s, 6H), 2.48 (s, 3H), 4.0 (t, 2H), 7.28 (d, 2H), 7.76 (d, 2H); MS m/e 221, 120, 92, 58 (base). colorless liquid. IR (neat) 1600, 1675 cm- 161 B. Photokinetic Techniques 1. General Procedure Glassware - All photochemical glassware (class A volumetric flasks and pipets) was cleaned by first washing with acetone twice, followed by soaking in hot distilled water containing Alconox detergent for 24 hours. Then the equipment was rinsed and soaked in hot distilled water for 2 days, changing the water every 12 hours. Syringes used for transferring solutions and Pyrex culture tubes used for irradiation were also cleaned in the same manner. All glassware was dried in a 150° oven used solely for drying photochemical glassware. Irradiation tubes were made by heating the previously cleaned Pyrex culture tubes (13 x 100 mm) near the tap and drawing them out to a uniform 15 mm length (2 mm neck). Sample Preparation - Solutions were prepared by either weighing the desired amount of compound directly into the volumetric flask and diluting to the mark with solvent or by pipetting an aliquot from a stock solution (make in the above manner) into a volumetric flask and diluting to the mark. A constant amount (2.8 m1) of the solutions were syringed into the constricted culture tubes. Usually hydrocarbon internal standard were used in irradiations, but when solubility was a problem, standards were added after photolysis by pipetting both photolyzed ketone and standard (known concentration) into vials before 80 analysis. 162 QggassingProcedgrg_- The filled irradiation tubes were attached to.a vacuum line (10'4 Torr) by means of one-hole rubber stoppers (size 00) attached to a manifold containing 12 stopcocks. The solu- tions were frozen by slow immersion in liquid nitrogen, followed by opening of the stopcocks. After pumping on the samples for 5-15 minutes (depending on sample) the stopcocks were closed and the solutions were allowed to thaw completely. This freeze-pump-thaw cycle was repeated two to four times (depending on sample) after which the tubes were sealed while still frozen using a torch. Pyrex tubes fitted to ground glass joints and a manifold con- taining 10 vacuum stopcocks with ground glass joints were used in Stern VOlmer quenching experiments involving the determination of room temperature phosphorescence lifetimes. Also, six 5-8 minute freeze-pump-thaw cycles were performed and the diffusion pump was employed in the last two cycles. Irradiation Procedure - Quantum yield and Stern Volmer quench- ing studies were performed by parallel irradiation of samples and actimometer in a merry-go-round apparatus immersed in a water bath maintained at 25°. A water-cooled Hanovia medium-pressure mercury lamp equipped with either an alkaline potassium chromate (0.002 M K20r04 and 1% K2603) filter solution to isolate the 313 nm band or Corning #7-83 filters to isolate the 366 nm band was used in the analyses. Analysis of Samples - All analyses were performed on a Varian Aerograph Series 1200 or Hy-Fi Model 550 gas chromatographs (flame 163 ionization detectors) equipped with Leeds and Northrup recorders and Infotronics CRS 309 digital integrators. 0n-column injection and nitrogen carrier gas (40 ml/min flow rate) were used in all analyses. The 1/8" aluminum columns used in the analyses are listed below. Columns #1,2: 4' and 6-1/2', respectively, 4% QF-l and 1% Carbo- wax 20 M on Aw-Chromosorb G, with 1% KOH added. Column #3: 8' 5% FFAP on Aw-Chromosorb P. Column #4: 3' 19.4% FFAP on Ali-Chromosorb P. Column #5: 5' 5% SE-30 on Chromosorb w. Column #6: 25' 25% 1,2,3-Tris (2-cyanoethyl)propane on Chromosorb P. GC response factors were determined by measuring the relative peak areas of products and standards of known concentrations. The ortho- and meta-substituted acet0phenones not available were assumed to have the same response factor as their para-isomers. The response factors determined are given below. AreaiMole (std; Standard/Product rea/Mole prod hexadecane/acetophenone 2.33:0.03 heptadecane/acetophenone 2.39 nonadecane/p-cyanoacetophenone 2.42:0.02 eicosane/p-cyanoacetophenone ‘ 2.64:0.03 eicosane/m—cyanoacetophenone 2.49:0.03 heneicosane/p-cyanoacetophenone 2.72:0.02 eicosane/p-carbomethoxyacetophenone 2.52:0.03 164 Area/Mole (std) Standard/Product Area/Mole (prod) eicosane/p-diacetylbenzene 2.56:0.04 heneicosane/p-acetylvalerophenone 1.82:0.02 docosane/p-acetylvalerophenone 1.93:0.03 tetracosane/p-acetylvalerophenone 2.03:0.04 eicosane/p-methoxyacetophenone 2.50:0.01 docosane/p-methoxyacetophenone 2.68:0.04 tridecane/p-trifluoromethylacetophenone 1.69:0.03 hexadecane/p-trifluoromethylacetophenone 2.01:0.02 n-octyl benzoate/p-acetyl B-dimethylaminoethyl benzoate 2.50:0.02 tetracosane/p-(3-dimethylaminopropoxy)acetophenone 2.35:0.05 Identification of Photoproducts - Samples were analyzed for acetophenone photoproducts, identified by comparison of GC reten- tion times with those of authentic samples under identical condi- tions. In general, the ortho- and meta-substituted acet0phenones were unavailable, and these acet0phenones were assumed to have nearly identical retention times as their para isomers. As a check, p- carbomethoxyacetophenone was also identified by GC/MS in the photolysis of p-carbomethoxyvalerophenone in acetonitrile. Usually two small broad peaks with slightly longer retention times than the parent ketones were evident in the GC traces, and these peaks were assumed to correspond to the isomeric cyclobutanols typically formed in the photolysis of phenyl alkyl ketones.28 The para-aminoketones were also identified by comparison of GC retention times with those of the appropriate aminoacetophenones 165 independently synthesized. m-2AB was assumed to have nearly the same GC retention time as the para isomer. Also, a 250 MHz 1H NMR spectra of the photolyzed sample from irradiation of p-2AB in acetonitrile showed the appearance of a singlet with the same chemical shift as the corresponding acetophenone methyl group. 2. Stern-Volmer Quenching Studies and Quantum Yields Usually stock solutions of ketone and internal standard were pre- pared in 10 ml volumetric flasks from which constant amounts were pipetted for both quenched and unquenched samples (1 ml/S ml volum- metric and 2 ml/10 ml volumetric, respectively). Also stock quencher solutions were made in 10 ml volumetric from which varying amounts (0.25 ml-3 ml) were pipetted. When necessary, stock solutions of additive (i.e., pyridine) were also prepared in 10 ml volumetric flasks. The various volumetric flasks were then filled to volume with solvent. Usually, three tubes without quencher and 6 tubes containing varying amounts of quencher were prepared. After the tubes were filled, degassed, and photolyzed, o°/¢ was obtained for each quenched solution by dividing the average GC photoproduct/ standard ratio for the unquenched tubes by the same ratio for the quenched tubes. A plot of oO/o versus quencher concentration enables calculation of triplet lifetime from the slope. Quantum yields were also obtained at the same time by parallel irradiation of an actinometer. The quantum yield of acetophenone formation for 0.05 M valerophenone in benzene is 0.315 and for 0.1 M 13 valerophenone in benzene is 0.33. Quantum yields can be calculated 166 as follows: 0 Quencher Tube: [X-Acetophenone] = [Standard] x R.F. x area X-AP/area standard Actinometer Tube; [Acetophenone] = [Standard] x R.F. x area AP/area standard ¢II = 0.33 ([X—Acetophenone]/[Acetophenone]) Maximum quantum yields were obtained by adding varying amounts of a stock solution of Lewis base to solutions of ketone and internal standard. Usually 0.5 M pyridine was sufficient to maximize the quantum yield and added pyridine had either no effect or slightly decreased the quantum yield. 3. Disappearance Yields Disappearance yields were determined by comparing the ketone concentration before and after irradiation. A known concentration of external'standard was added to both photolyzed and unphotolyzed samples. Since the initial ketone concentration was known, then the GC response factor was calculated and used to calculate the ketone concentration after photolysis. The disappearance yield was cal- culated as follows: 167 AKetone = [KetoneJinitial - [Ketone]final AKetone a = 0.33 P act -K All samples were taken to 20% or more conversion in order to minimize the error involved in the measurements and valerophenone was used as actinometer. 4. Intersystem CrossingYields The intersystem crossing yields for p-cyanoacetophenone and p- carbomethoxyvaler0phenone were obtained by sensitizing the iso- merization of cis—1,3-pentadiene. Tubes containing 0.04 M ketone with varying amounts of cis 1,3-pentadiene were irradiated (313 nm) in parallel with 0.06 M acetophenone or valerophenone, respectively, and varying amounts of cis 1,3-pentadiene as actinometers. A plot of al¢isom versus l/[cisl,3-pentadiene] gives a linear correlation in which l/intercept equals ¢ISC' a B'Actmuencher]Act _. 9 ¢isom BKetoneEQue"Cher]Ketone where a is the photostationary state for quencher isomerization (a = 0.55 for cis 1,3-pentadiene)14 and B' is the fraction of newly formed isomer corrected for back-reaction. 0.55 3' = 0.55 1n T6573 , where a = ma "a“ area trans + area cis 168 5. Photoreduction Photoreduction experiments on p-cyanoacetophenone were performed by preparing stock solutions of both ketone and donor and by adding varying amounts of donor to a constant amount of ketone (0.05 M). After photolysis, the amount of donor coupling product was determined and a plot of llo versus l/[donor] gave a linear cor- coupling prod relation with a slope/intercept equal to kd/kr' Stern-Volmer quench- ing experiments involving varying the amount of naphthalene quencher with a constant amount of ketone and donor gave a linear correla- tion when polo versus [quencher] was plotted (formation of coupling photoproduct was monitored). Since the lifetime, T, can be deter- mined from the slope and 1/T = kd + kr’ then both kd and kr could be determined from these experiments. C. Spectra 1. Phosphorescence Emission Spectra Phosphorescence spectra were recorded on a Perkin-Elmer MPF-44A Fluorescence Spectrbphotometer equipped with a Differential Cor- rected Spectra Unit and Hitachi PhoSphorescence Accessory. Spectra were run on 10'4 M.ketone in various solvent glasses at 77°K using a quartz dewar and 5 mm quartz tubes. The corrected emission scan mode, ratio measurement mode, and DC photometric mode were used. Excitation and emission slit widths were typically 8 and 4 nm, respectively, and spectra were recorded at a scan rate of 120 nm/min. 169 Various sample sensitivities, excitation wavelengths, and emission responses (0.3 - 3 sec) were used, depending on sample. 2. Electronic Absorption Spectra Ultraviolet absorption spectra were recorded on a Cary 219 spectrophotometer. MCB Omnisolv heptane was used as solvent. Ex- tinction coefficients at 313 nm for various ketones were determined on a Gilford-Beckman spectrophotometer. 3. Infrared Spectra IR spectra were recorded on a Perkin-Elmer Model 237 B grating infrared spectr0photometer. Samples were run as thin films or KBr pellets and polystyrene (1601.4, 2850.7 cm") was used to calibrate each spectrum. 4. 1H NMR Spectra 1 Routinely, H NMR spectra of CDCl3 solutions (1% TMS) of the various ketones were recorded on a Varian T-60 spectrometer. 1H NMR spectra (250 MHz) were taken of the Fourier transformed following amino ketones, since similar chemical shifts resulted in overlapping peaks in the T-60 spectra: p—2VB: (CDC13) 60.960 (t, 3H); 1.42 (sextet, 2H); 1.73 (quin- tet, 2H); 2.45 (s, 6H); 2.73 (t, 2H); 2.99 (t, 2H); 4.46 (t, 2H); 8.01 (d, 2H); 8.12 (d, 2H). 170 m-2VB: (CDC13) 60.963 (t, 3H); 1.42 (sextet, 2H); 1.74 (quintet, 2H); 2.36 (s, 6H); 2.75 (t, 2H); 3.01 (t, 2H); 4.48 (t, 2H); 7.55 (t, 1H); 8.22 (m, 2H); 8.61 (m, 1H). p-3VB: (CDCls)60.958 (t, 3H); 1.42 (sextet, 2H); 1.73 (quintet, 2H); 1.98 (quintet, 2H); 2.26 (s, 6H); 2.44 (t, 2H); 2.99 (t, 2H); 4.41 (t, 2H); 8.01 (d, 2H); 8.12 (d, 2H). p-288: (CDC13) 62.83 (S, 6H); 2.77 (t, 2H); 4.49 (t, 2H); 7.50 (m, 1H); 7.60 (m, 2H); 7.82 (t, 4H); 8.17 (d, 2H). p-3VE: (CDCl3) 60.945 (t, 3H); 1.38 (sextet, 2H); 1.72 (quin- tet, 2H); 1.97 (quintet, 2H); 2.25 (s, 6H); 2.45 (t, 2H); 2.90 (t, 2H); 4.08 (t, 2H); 6.92 (d, 2H); 7.93 (d, 2H). The spectra were recorded on a Bruker NM 250 spectrometer by Michael A. Meador. Also, 250 MHz spectra of p-ZBB (1.0 x 10'4 M) in carbon 4 tetrachloride with 1% C606 and 10‘ M tetrachloroethane internal standard were recorded by M. A. Meador. 5. Mass Spectra Mass spectra were run on a Finnigan 4000 GC/MS using the direct inlet mode by Ernest Oliver. 6. Cyclic Voltammetry Reduction potentials were measured for various ketones (10'4 M) in Aldrich gold label acetonitrile (0.1 M TEAP) relative to SCE at a hanging mercury drop electrode with platinum auxillary electrode by cyclic voltammetry using a PAR 174A analyzer. The half-wave 171 reduction potentials were independent of sweep rate between 100-500 mV/sec, with reversibility increasing with increasing scan rates. Most ketones showed a quasi-reversible, if not completely reversible wave . APPENDIX The Appendix contains the raw experimental data used to cal- culate the photokinetic parameters. The data are contained in tables which include: concentrations of ketone, quencher, standards, valerophenone actinometer, and photoproducts f0rmed; product/standard ratios; quencher; solvent and additive (if any); and GC column condi- tions. 80th descriptions of the columns and GC response factors are contained in the experimental section. In all cases valerophenone in benzene was used as actinometer and was analyzed on column #3 at‘»l30°. The GC response factor for acetophenone versus C16 is 2.3 and for acetophenone versus C14 is 2.0. All quantum yields were performed at 313 nm in a merry-go- round apparatus. Quenchers 2,5-dimethylhexa-2,4-diene, 1,3-pentadiene, and triethylamine were referred to simply as hexadiene, pentadiene, and Et3N, respectively. All runs using acetonitrile as solvent con- tained 2% water, unless specifically stated as dry acetonitrile. l72_ REFERENCES 173 Table 20. Quenching of 0.039 M Valerophenone by Hexadiene in Benzene. a k T = 47 q AP/C16 [0]. M Area Ratiob [AP], 10'3 M ¢°I¢ 0.0 2.10 2.38 --- 0.0050 1.69 1.92 1.24 0.0100 1.40 1.59 1.50 0.0200 1.06 1.20 1.99 0.0400 0.703 0.799 2.98 0.0600 0.566 0.643 3.71 aR1, 313 nm, 50 min. b[c163 = 4.94 x 10'4 M; column #3, 120°. 174 Table 21. Quenching of Valerophenone by Hexadiene in Acetonitrile.a Run #1: qu = 61, 011 = 0.87b AP/c16 [0], M Area Ratioc [AP], 10'3 M ¢°I¢ 0.0 .1.31 1.84 ---- 0.0034 1.12 1.57 1.17 0.0068 0.796 1.12 1.64 0.0136 0.655 0.919 2.00 0.0204 0.609 0.854 2.15 0.0272 0.511 0.717 2.56 0.0408 0.395 0.554 3.32 a0.041 M ketone; R1. 313 nm, 25 min. b0.10 M vp actinometer: AP/c16 area ratio = 0.120; [016] = 2.69 x -3 10 M. c[016] = 6.10 x 10‘4 M; Column #1, 90°. Run #2: k T = 64 q AP/c16 [0], M Area Ratioc [AP], 10'3 M ¢°I¢ 0.0 2.19 2.05 ---- 0.00730 1.51 1.41 1.45 0.0150 1.17 1.00 1.87 0.0220 0.903 0.845 2.42 0.0290 0.746 0.698 2.93 0.0440 0.546 0.511 4.00 20.037 M ketone; RT, 313 nm, 25 min. [017] = 3.90 x 10'4 M; column #1. 105°. a Table 22. Quenching of Valerophenone by Triethylamine in Benzene. Run #1: kqt = 11 AP/C ‘7 b -3 o [Q], M Area Ratio [AP], 10 M 0 /¢ 0.0 0.755 1.39 --- 0.00714 0.701 1.29 1.08 0.0143 0.660 1.21 1.14 0.0286 0.562 1.03 1.34 0.0571 0.448 0.824 1.68 0.0857 0.383 0.704 1.97 a0.021 M ketone; 0.50 M pyridine; RT, 313 nm, 20 min. b[on] = 7.66 x 10'4 M; column #1, 100°. . Run #2: qu = 12 AP/C ‘7 b -3 0 [Q], M Area Ratio [AP], 10 M ¢ /¢ 0.0 2.21 2.07 --- 0.0139 1.97 1.84 1.12 0.0278 1.66 1.55 1.34 0.0555 1.32 1.24 1.68 0.0833 1.13 1.06 1.96 a0.020 M ketone; 0.50 M pyridine; RT, 313 nm, 20 min. b[017] = 3.90 x 10'4 M; column #1, 100°. 176 Table 23: Quenching of Valerophenone by Triethylamine in Aceto- nitrile. Run #1: k T = 13, 911 = 0.85 q AP"317 [0], M Area Ratiob [AP], 10‘3 M ¢°/¢ 0.0 1.16 2.75 ---- 0.0101 1.02 2.42 1.13 0.0202 0.929 2.21 1.24 0.0403 0.778 1.85 1.49 0.0605 0.649 1.54 1.78 0.0807 0.567 1.35 2.04 0.121 0.457 1.08 2.53 a0.041 M ketone; RT, 313 nm. b0.099 M vp actinometer; AP/c17 area ratio = 0.349; [017] = 1.25 x 10-3 M. c[CW] = 9.89 x 10'4 M; column #3, 145°. . - g *5 Run #2. kqt - 14, 411 0.85 AP/c16 [0], M Area Ratioc [AP], 10‘3 M o°/o 0.0 1.07 2.30 ---- 0.00476 1.00 2.15 1.06 0.00952 0.963 2.07 1.11 0.0190 0.803 1.73 1.33 0.0286 0.781 1.68 1.37 0.0381 0.705 1.52 1.52 0.0571 0.599 1.29 1.78 a0.042 M ketone; RT, 313 nm, 25 min. 20.11 M V? actinometer: AP/c16 ratio = 0.443; [016] = 8.80 x 10-4 M. [016] = 9.36 x 10-4 M; column #3, 145°. 177 Table 24. Quenching of 0.040 M Butyrophenone by Hexadiene in Benzene.a. - - b k t - 560, 011 - 0.23 q AP/c16 [0], M Area Ratioc [AP], 10"3 M ¢°/¢ 0.0 3.39 5.44 ---- 0.00050 2.53 4.06 1.34. 0.0010 2.15 3.45 1.57 0.0015 1.91 3.07 1.82 0.0020 1.63 2.62 2.08 aR1, 313 nm, 1 hr. b0.10 M VP actinometer: AP/c16 area ratio = 0.773; [c161 = 2.56 -3 x 10 M. c[c161 - 6.98 x 10'4 M; column #3, 100°. 178 Table 25. Quenching of o-Cyanovalerophenone by Hexadiene in Benzene.a . - g b Run #1. kq; - 21, 011 0.15 AP/Cz] [Q], M Area Ratioc [AP], 10'3 cold 0.0 0.765 2.81 ---- 0.0071 0.669 2.46 1.14 0.0141 0.591 2.17 1.30 0.0282 0.498 1.83 1.54 ‘ 0.0423 0.389 1.43 1.97 0.0564 0.344 1.26 2.23 a‘0.040 M ketone; RT, 313 nm. b0.25 M VP actinometer: AP/C16 area ratio a 0.286; [€16] = 9.72 x 10'3 M; («III a 0.35 for 0.25 M VP in benzene). “[c2]] = 1.36 x 10‘3 M; column #3, 195°. . g e b Run #2. qu 23, 411 0.15 AP/C21 - [0], M Area Ratio“ [AP], 10 3 M ¢°I¢ 0.0 0.752 2.74 ---- 0.0129 0.540 1.97 1.39 0.0258 0.466 1.70 1.61 0.0387 0.390 1.42 1.93 0.0516 0.357 1.30 2.11 a0.04 M ketone; RT, 313 nm, 2.5 hrs. b0.25 M VP actinometer: AP/C16 area ratio = 0.326; [C16] = 8.39 x 10'3 M. “[c21] = 1.35 x 10'3 M; column #3, 195°. 179 Table 26. Quenching of 0.040 M o-Cyanovalerophenone by Pentadiene in Acetonitrile.a k T = 33 o = 0 54b q ’ II ' AP/C 2] c -3 0 [Q], M Area Ratio [AP], 10 M 0 /¢ 0.0 1.70 2.44 ---- 0.0050 1.64 2.36 1.04 0.0100 1.37 1.97 1.24 .0.0200 1.00 1.44 1.70 0.0300 0.843 1.21 2.02 0.0400 0.664 0.954 2.56 °RT, 313 nm, 1 hr. b 0.10 M VP actinometer: x 10'3 M. “[021] = 5.32 x 10' 4 AP/C16 area ratio = 0.160; [C16] = 4.06 M; column #2, 130°. 180 Table 27. Quenching of m-Cyanovalerophenone by Hexadiene in Benzene.a Run #1: k t = 19, “II = 0.17b q AP/CZI [0], M Area Ratio“ [AP], 10"3 M ¢°/¢ 0.0 2.73 9.66 ---- 0.0210 1.92 6.81 1.43 0.0420 1.55 5.50 1.76 0.0630 1.24 4.40 2.21 0.0840 1.07 3.80 2.56 0.105 0.894 3.17 3.06 a0.041 M ketone; RT, 313 nm, 3.5 hrs. b0.050 M VP actinometer: AP/c16 area ratio = 5.06; [016] = 1.50 -3 x 10 M. “[021] = 1.31 x 10"3 M; column #4, 200°. Run #2: k r = 19. “II = 0.19b q AP/c19 [0], M Area Ratio“ [AP], 10'3 ¢°I¢ 0.0 1.45 ' 2.35 ---- 0.0102 1.17 1.90 1.24 0.0204 1.04 1.69 1.40 0.0306 0.924 1.50 1.57 0.0409 0.824 1.34 1.76 0.0511 0.739 1.12 1.96 °0.040 M ketone; RT, 313 nm, 8 hrs. b0.060 M VP actinometer: AP/c14 area ratio = 0.575; [014] = 3.25 x 10'3 M. c[€19] = 6.76 x 10'4 M; column #1, 150°. '181 Table 28. Quenching of 0.039 M m-Cyanovalerophenone by Hexadiene in Acetonitri1e.a qu = 20, 011 = 0.63b AP/C [0], M Area R5210“ [AP], 10‘3 M o°/o 0.0 0.763 1.87 ---- 0.00641 0.676 1.65 1.13 0.0128 0.598 1.46 1.26 0.0256 0.518 1.27 1.47 0.0385 0.430 1.05 1.77 0.0529 0.380 0.930 2.01 0.0769 0.296 0.725 2.58 “R1. 313 nm. b0.10 M VP actinometer: AP/c16 area ratio = 0.111; [016] = 3.80 -3 x 10 M. “[c19] = 1.02 x 10'3 M; column #1, 142°, N2 on 60 ml/min. 182 Table 29. Quenching of m-Cyanovalerophenone by Triethylamine in Benzene.a Run #1- k T = 22 o = 0 23b 6 = 0 65b ' q ’ II ' ’ ma ' AP/C 20 c -3 0 [Q], M Area Ratio [AP], 10 M 6 /¢ 0.0 1.37 2.11 ---- 0.0186 1.04 1.60 1.32 0.0372 0.778 1.20 1.77 0.0745 0.504 0.776 2.73 0.112 0.405 0.624 3.43 0, 0 pyr. 0.482 0.742 ---- a0.040 M ketone; 0.50 M pyridine; RT, 313 nm, 40 min. b0.10 M VP actinometer: AP/c16 area ratio = 0.348; [016] = 1.28 x 10"3 M. “[020] = 6.16 x 10‘4 M; column #1, 151°. Run #2: qu = 22, “II = 0.22,b AP/c20 [0], M Area Ratio“ [AP], 10'3 M ¢°I¢ 0.0 1.21 1.91 ---- 0.051 0.542 0.854 2.23 0.076 0.441 0.695 2.73 0.101 0.373 0.588 3.23 0.127 0.322 0.507 3.75 0, 0 pyr 0.662 1.04 ---- a0.040 M ketone; 0.049 M pyridine; RT, 313 nm, 1 hr. 0.10 M VP actinometer: AP/C16 area ratio b x 10'3 M. “[020] = 6.30 x 10 M; column #1, 148°. 0.0959; [615] = 7.02 183 Table 30. Quenching of m-Cyanovalerophenone by Triethylamine in Acetonitri1e.a Run #1: qu = 10, 411 = 0.73b AP":20 [0], M Area Ratio“ [AP], 10"3 M ¢°/¢ 0.0 1.24 2.01 ---- 0.0124 1.14 1.85 1.09 0.0247 0.953 1.54 1.31 0.0494 0.833 1.35 1.49 0.0741 0.716 1.16 1.74 0.0988 0.625 1.01 1.99 0.148 0.483 0.783 2.58 a0.040 M ketone; RT, 313 nm. b0.11 M VP Actinometer: AP/c16 area ratio = 0.358; [016] = 1.15 x 10'3 M. “[020] = 6.48 x 10'4 ; column #1, 138°. Run #2: k T = 10 q AP/619 [Q], M Area Ratiob [AP], 10'3 M polo 0.0 1.37 1.87 ---- 0.0091 1.29 1.77 1.06 0.0182 1.20 1.64 1.14 0.0365 0.978 1.34 1.40 0.0548 0.866 1.19 1.58 0.0730 0.814 1.11 1.68 0.109 0.618 0.846 2.21 a0.036 M ketone; RT, 313 nm. b[C19]=5.95x10-4 M; column #1, 140°. 184 Table 31. Quenching of p-Cyanovalerophenone by Hexadiene in Benzene. . - _ b Run #1. qu - 75, 411 - 0.22 AP/C 20 c -3 0 [Q], M Area Ratio [AP], 10 M o lo 0.0 0.772 2.33 ---- 0.00586 0.513 1.55 1.51 0.0117 0.423 1.28 1.82 0.0234 0.285 0.860 2.71 0.0352 0.212 0.639 3.64 0.0469 0.168 0 507 4.60 a0.042 M ketone; RT, 313 nm, 2 hrs. b0.10 M VP actinometer: AP/C16 area ratio = 0.182; [C16] = 8.21 x 10'3 M. “[020] = 1.16 x 10‘3 M; column #3. 190°. Run #2- k T e 73 o . 0 20b . q , II . AP/c19 [0], M Area Ratio“ [AP], 10'3 M ¢°l¢ 0.0 2.30 3.54 ---- 0.0193 1.01 1.55 2.28 0.0579 0.471 0.725 4.90 0.0772 0.348 0.536 6.61 0.0964 0.274 0.422 8.24 a0.041 M ketone; RT, 313 nm, 8 hrs. b0.050 M VP actinometer: AP/c14 area ratio = 0.621; [014] = 4.08 x 10‘3 M. “[019] = 5.92 x 10"4 M; column #3, 190°. 185 Table 32. Quenching of 0.040 M p-Cyanovalerophenone by Hexadiene in Acetonitri1e.a - a b k c - 87, 411 0.80 q AP/c19 [0], M Area Ratio“ [AP], 10‘3 M o°/o 0.0 0.950 2.26 ---- 0.00419 0.667 1.59 1.42 0.0168 0.406 0.966 2.34 0.0251 0.286 0.680 3.32 0.0335 0.246 0.585 3.84 0.0503 0.178 0.423 5.33 °R1, 313 nm, 1/2 hr. b0.10 M VP actinometer: AP/C16 area ratio = 0.191; [C16] = 2.12 x 10'3 M. c = - [019] 9.91 x 10 4 M; column #1, 142°. 186 Table 33. Quenching of p-Cyanovalerophenone by Triethylamine in Benzene.a Run #1: k T = 86 q AP/C 2° b -3 0 [Q], M Area Ratio [AP], 10 M ¢ /¢ 0.0 1.41 1.06 ---- 0.00934 1.53 1.15 0.92 0.0187 1.09 0.822 1.30 0.0374 0.658 0.496 2.15 0.0561 0.484 0.365 2.92 a0.021 M ketone; 0.50 M pyridine; RT, 313 nm, 20 min. b[020] = 2.90 x 10'4 M; column #1, 150°. . - = b Run #2. k T ‘ 969 ¢0.25 M pyr 0.37 q AP/c20 3 [0], M Area Ratio [AP], 10' .M ¢°/¢ 0.0 1.39 1.41 ---- 0.0046 2.09 2.12 0.66 0.0093 1.63 1.65 0.85 0.0139 1.30 1.32 1.07 0.0186 1.06 1.07 1.31 0.0316 0.665 0.674 2.09 0.0557 0.532 0.539 2.61 a0.040 M ketone; 0.25 M pyridine; RT, 313 nm, 30 min. b0.10 M VP actinometer: AP/c16 area ratio = 0.280; [C16] = 1.94 x -3 10 M. “[020] = 3.90 x 10’4 M; column #1, 150°. 187 Table 33. Continued. Run #3: k T = 91 q AP/C [0], M Area Rigiob [AP], 10‘3 M ¢°I¢ 0.0 1.25 1.01 ---- 0 0093 1.57 1.27 0.80 0 0187 1.03 0.836 1.21 0.0373 0.794 0.644 1.58 0.0560 0.417 0.338 3.00 a0.020 M ketone; 0.50 M pyridine; RT, 313 nm, 20 min. b[020] = 3.12 x 10‘4 M; column #1, 150°. 188 Table 34. Quenching of 0.042 M p-Cyanovalerophenone by Low Con- centrations of Triethylamine in Benzene.a AP/c20 _ [0], M Area Ratiob [AP], 10'3 M o°/o 0.0 ' 1.44 1.88 ---- 0.0012 1.81 2.36 0.80 0.0024 2.29 2.99 0.63 0.0048 1.77 2.31 0.81 0.0072 1.67 2.18 0.87 0.0096 1.57 2.05 0.92 0.0143 1.42 2.05 1.0 °0.54 M pyridine; RT, 313 nm, 50 min. b[c 5.02 x 10‘4 M; column #1, 135°. 20] = 189 Table 35. Quenching of 0.037 M p-Cyanovalerophenone by Triethyl- amine in Acetonitri1e.a qu = 92, °II = 0.67b AP/c19 [0], M Area Ratio“ [AP], 10"3 M ¢°I¢ 0.0 0.914 1.66 ---- 0.000664 0.904 1.64 1.01. 0.00133 0.858 1.56 1.06 0.00266 0.769 1.40 1.19 0.00398 0.694 1.26 1.32 0.00531 0.657 1.19 1.39 0.00797 0.579; 1.05 1.58 aR1, 313 nm. b 10'3 M. “[019] = 7.56 x 10'4 M; column #3, 180°. 0.12 M VP actinometer: AP/C16 area ratio = 0.67; [C16] = 3.49 x Table 36. Quenching of 0.041 M p-Cyanobuty in Benzene.a rophenone by Hexadiene qu = 360, 411 = 0.12b AP/C [0], M Area Rigio“ [AP], 10'3 M o°/o 0.0 1.66 3.00 ---- 0.00050 1.42 2.56 1.17 0 0010 1.22 2.22 1.36 0.0020 1.17 2.11 1.76 0.0040 0.654 1.18 2.54 0.0060 0.499 0.900 3.33 “R1, 313 nm, 2 hrs. b 10'3 M. “[020] = 6.94 x 10'4 M; column #2, 110°. 0.10 M VP actinometer: AP/C16 area ratio = 1.43; [C16] = 2.56 x 191 Table 37. Quenching of 0.040 M p-Cyanobutyrophenone by Hexadiene in Benzene.a kqt = 435, “II = 0.12b AP/c [0], M Area Rigioc [AP], 10'3 M o°/o 0.0 1.88 3.71 ---- 0.000248 1.61 3.17 1.17 0.000496 1.48 2.92 1.27 -0 000993 1.23 2.42 1.52 0.00149 1.11 2.19 1.69 0.00199 1.04 2.05 1.80 0.00298 0.87 1.71 2.16 aR1, 313 nm, 2-1/2 hrs. b0.10 M VP actinometer: AP/c16 area ratio = 2.26; [016] = 1.94 x 10‘3 M. “[020] = 7.58 x 10'4 M; column #2, 110°. 192 Table 38. Quenching of 0.037 M p-Cyano-y-Methylvalerophenone by Hexadiene in Benzene.a - - b qu - 18’ ¢II " 0.13 AP/C 20 c -3 0 [Q], M Area Ratio [AP], 10 M o lo 0.0 0.753 1.50 ---- 0.0050 0.644 1.28 1.17 0.0100 0.600 1.20 1.25 0.0201 0.583 1.16 1:32 0.0301 0.461 0.918 1.63 3R1, 313 nm. 2 hrs. b0.10 M VP actinometer: AP/c16 area ratio = 0.847; [016] = 1.99 x10'3 M. “[620] = 7.66 x 10'4 M; column #2, 120°. '193 Table 39. Quenching of o-Carbomethoxyvalerophenone by Hexadiene in Benzene. ' 3 = b Run #1. qu 138, 411 0.04 AP/C 20 c -4 o [0]. M Area Ratio [AP], 10 M a /4 0.0 0.955 7.26 ---- 0.00142 0.837 6.36 1.14 0.00283 0.724 5.50 1.32 0.00567 0.520 3.95 1.84 0.00850 0.440 3.34 2.17 0.0113 0.366 2.78 2.61 0.0170 0.277 2.11 3.45 a0.043 M ketone; RT, 313 nm, 2 hrs. b0.10 M VP actinometer: AP/c16 area ratio = 1.16; [016] = 2 x -3 10 M. “[020] = 3.04 x 10'4 M; column #1, 140°. Run #2: qu = 150, AP/C 20 b -3 0 [Q], M Area Ratio [AP], 10 M p [0 0.0 3.61 3.75 ---- 0 0101 1.49 1.55 2.42 0.0203 0.917 0.954 3.94 0.0304 0.695 0.723 5.19 0.0405 0.493 0.513 7.32 a0.051 M ketone; RT, 313 nm, 1-1/2 hrs. b[C20] = 4.16 x 10'4 M; column #3, 180°. 194 Table 39. Continued. ..Run #3: k T = 120 q AP/C [Q], M Area Rigiob , [AP], 10'3 M ¢°/¢ 0.0 3.71 1.50 ---- 0.00518 2.30 0.932 1.62 0.0102 1.65 0.668 2.25 0.0154 1.35 0.547 2.75 0.0205 1.12 0.454 2.03 0.0256 0.894 0.362 4.15 a0.042 M ketone; RT, 313 nm, 2 hrs. b[020] = 1.62 x 10'4 M; column #3, 180°. 195 Table 40. Quenching of 0.041 M o-Carbomethoxyvalerophenone by Hexa- diene in Acetonitri1e.a - _ b k T " 338, ¢II ‘ 0.19 q AP/C [0], M Area Rigioc [AP], 10.3 M oolo 0.0 1.28 1.62 ---- 0.000772 0.987 1.25 1.30 0.00154 0.829 1.05 1.54 0.00309 0.625 0.789 2.05 0.00463 0.482 0.609 2.66 0.00617 0.422 0.533 3.03 0.00926 0.304 0.384 4.22 °R1, 313 nm, 2-1/2 hrs. b0.10 M VP actinometer: AP/C16 area ratio = 0.340; [C16] = 3.58 -3 x 10 M. 4 “[020] = 5.05 x 10' M; column #1, 125°. 196 Table 41. Quenching of o-Carbomethoxyvalerophenone by Triethyl- amine in Benzene.a Run #1: kq; = 60, “max = 0.13 AP/C 20 c -3 0 [Q], M Area Ratio [AP], 10 M 4 /¢ 0.0 1.24 2.41 ---- 0.00745 1.08 2.10 1.14 0.0149 0.854 1.66 1.46 0.0298 0.552 1.07 2.25 0.0447 0.415 0.807 3.00 0.0596 0.328 0.638 3.80 “0.041 M ketone; RT, 313 nm, 4 hrs. b0.11 M VP actinometer: AP/c16 area ratio = 1 14; [C16] = 2.43 x 10‘3 M. “[czo] = 7.78 x 10‘4 M; column #1, 135°. Run #2: qu = 57, ¢max = 0.10 AP/C 20 c -3 0 [0], M Area Ratio [AP], 10 M 6 lo 0.0 1.89 2.78 ---- 0.00365 1.88 2.76 1.01 0.00729 1.86 2.73 1.03 0.0146 1.58 2.32 1.20 0.0292 1.04 1.53 1.82 0.0438 0.785 1.15 2.41 “0.044 M ketone; RT, 313 nm, 4 hrs. 0.11 M VP actinometer: b x10'3 M. “[020] = 5.88 x 10‘4 AP/C16 area ratio = M; column #1, 135°. 0.963; [C16] = 4.28 Table 42. Quenching of o-Carbomethoxyvalerophenone by Triethylamine in Acetonitri1e.a Run #1- k c . 89 o = 0 11b 0 q ’ II 0 AP/C 20 c -3 0 [Q], M Area Ratio [AP], 10 M 4 [4 0.0 1.00 1.76 ---- 0.00251 0.826 1.45 1.21 0.00502 0.725 1.27 1.38 0.0100 0.55 0.974 1.81 0.0151 0.427 0.749 2.35 0.0201 0.350 0.614 2.87 0.0301 0.265 0.465 3.78 “0.041 M ketone; RT, 313 nm, 4 hrs. b0.1; M VP actinometer: AP/c16 area ratio = 0.661; [C16] = 3.36 x 10- M. 4 c[c201 = 7.02 x 10' M; column #1, 131°. . - _ b Run #2. kqt - 78, 411 - 0.10 AP/c20 [0], M Area Ratio“ [AP], 10‘4 M ¢°/¢ 0.0 0.544 9.47 ---- 0.00135 0.495 8.61 1.10 0.00270 0.459 7.99 1.19 0.00540 0.392 6.82 1.39 0.00809 0.335 5.83 1.62 0.0108 0.294 5.12 1.85 0.0162 0.242 4.21 2.24 “0.041 M ketone; RT, 313 nm, 1 hr, 40 min. 0.1 M VP actinometer: 10' M. C[C20] = 6.96 x 10‘4 M; column #1, 135°. b AP/C16 area ratio =.0.351; [C16] = 3.75 x 198 Table 43. Quenching of m-Carbomethoxyvalerophenone by Hexadiene in Benzene. Run #1: k r = 19. 611 = 0.24b q AP/c20 [0], M Area Ratio“ [AP], 10'3 M ¢°/¢ 0.0 1.02 2.08 ---- 0.0103 0.857 1.74 1.19 0.0206 0.721 1.47 1.41 0.0413 0.569 1.16 1.76 0.0619 0.458 0 932 2.22 0.0826 0.398 0.810 2.56 “0.049 M ketone; RT, 313 nm, 1-1/2 hrs. b0.1% M VP actinometer: AP/C16 area ratio = 0.276; [C16] = 4.42 x 10‘ M. “[czo] = 8.14 x 10'4 M; column #3, 185°. . _ _ b AP/C 20 c -3 0 [Q], M Area Ratio [AP], 10 M o lo 0.0 1.28 2.58 ---- 0.0110 1.11 2.24 1.15 0.0220 0.954 1.92 1.34 0.0450 0.742 1.50 1.72 0.0670 0.578 1.17 2.21 “0.050 M ketone; RT, 313 nm, 1-3/4 hrs. b0.10 M VP actinometer: AP/c16 area ratio = 0 349; [016] = 4.33 x -3 10 M. “[020] = 8.07 x 10'4 M; column #3, 190°. 199 Table 44. Quenching of m—Carbomethoxyvalerophenone by Pentadiene in Acetonitrile.a Run #1: qu = 21, “II = 0.90b AP"321 [Q], M Area Ratioc [AP], 10'3 M polo 0.0 2.06 ’ 5.72 ---- 0.0100 1.61 4.47 1.28 0 0200 1.39 3.86 1.48 0.0400 1.10 3.05 1.87 0.0500 0.991 2.75 2.08 0.0600 0.894 2.48 2.30 0.0800 0.779 2.16 2.64 0.100 0.654 1.81 3.15 “0.040 M ketone; RT, 313 nm, 25 min. b0.10 M VP actinometer: AP/cl6 area ratio = 0.204; [C16] = 3.80 x 10"3 M. c[c2l] = 1.11 x 10‘3 M: column #2, 130°. Run #2: qu = 20, “II = 0.90b AP/c21 [0], M . Area Ratio“ [AP], 10‘3 M ¢°/¢ 0.0 2.96 4.49 ---- 0 0100 2.53 3.84 1.17 0.0200 2.15 3.26 1.38 0.0400 1.59 2.41 1.86 0.0600 1.30 . 1.97 2.28 0.0800 1.15 1.75 2.58 0.100 1.05 1.59 2.82 “0.040 M ketone; RT, 313 nm, 30 min. b0.10 M VP actinometer; AP/c16 area ratio = 0 313; [“16] = 1.99 x 10-3 M. c[02l] = 6.07 x 10-4 M; colunn #2, 140°. 200 Table 45. Quenching of 0.040 M m—Carbomethoxyvalerophenone by Tri- ethylamine in Benzene.a qu = 25, oll = 0.25,b omax = 0.54b AP/c [0]. M Area Rigioc [AP], 10"3 M o°/o 0.0 1.92 3.53 ---- 0.0251 1.53 2.82 1.26 0.0502 1.10 2.02 1.74 0.0753 0.932 1.71 2.06 0 100 0.707 1.30 2.72 0.151 0.521 0.959 3.69 0, 0 pyr 0.898 1.65 ---- “0.50 M pyridine; RT, 313 nm, 30 min. b0.10 M VP actinometer: AP/c16 area ratio = 0 540; [C16] = 1.72 x 10'3 M. c[c201 = 7.36 x 10' 4 M; column #1, 140°. 201 Table 46. Quenching of p-Carbomethoxyvalerophenone by Hexadiene in Benzene.“ Run #1: qu . 44, all = 0.19b AP/c20 [0], M Area Ratio“ [AP], 10‘3 M ¢°/¢ 0.0 0.841 1.73 ---- 0.00397 0.740 1.52 1.14 0.00794 0.605 1.24 1.39 0.0159 0.507 1.04 1.66 0.0238 0.400 0.822 2.10 0.0318 0 348 0.715 2.41 “0.050 M ketone; RT, 313 nm. b0.10 M VP actinometer: AP/C16 area ratio = 0.264; [Cl6] = 4.90 x 10-3M. “[020] = 8.22 x 10‘4 M; column #3, 190°. Run #2: ch = 40, “II = 0.19b AP/c20 [0], M Area Ratio“ [AP], 10'3 M ¢°/¢ 0.0 1.18 1.82 ---- 0.00327 1.06 1.63 1.12 0.00654 0.857 1.32 1.38 0.0131 0.885 1.36 1.34 0.0196 0.652 1.00 1.82 0.0262 0.619 0.953 1.91 0.0393 0.486 0.748 2.44 a0.041 M ketone; RT, 313 nm, 1 hr. b0.l; M VP actinometer: AP/C16 area ratio = 0.452; [C16] = 3.09 x 10‘ M. 4 “[020] = 6.16 x 10' M; column #1, 145°. 202 Table 47. Quenching of p-Carbomethoxyvalerophenone by Hexadiene in Acetonitri1e.a Run #1: k I = 63 q AP/Czo - [0], M Area Ratiob [AP], 10 3 M ¢°/¢ 0.0 1.62 2.97 ---- 0.00323 1.33 2.44 1.33 0.00647 1.09 2.00 1.49 0 0129 0.875 1.61 1.85 0.0194 0.748 1.37 2.17 0.0259 0.597 1.10 2.71 0.0388 0 496 0.910 3.26 “0.041 M ketone; RT, 313 nm, 30 min. b[020] = 7.34 x 10'4 M; column #1, 140°. . _ - b Run #2. kq; - 53, all 0.52 AP/C 20 c -3 0 [Q], M Area Ratio [AP], 10 M a [a 0.0 1.21 2.08 ---- 0.0050 1.02 1.75 1.19 0 0100 0.766 1.31 1.58 0.0200 0.568 0.974 2.13 0 0300 0.449 0.770 2.70 0.0400 0.403 0.691 3.01 0.0600 0.301 0.516 4.02 “0.040 M ketone; RT, 313 nm, 30 min. 0.10 M VP actinometer: AP/C16 area ratio = 0.204; [Cl6] = 2.83 b x 10'3 M. c[C20] = 6.86 x 10"4 M; column #3, 160°. 203 Table 48. Quenching of p-Carbomethoxyvaler0phenone by Triethyl- amine in Benzene.a Run #1: k T = 47, all = 0.22b a x = 0.32b q ma AP/c20 [0], M Area Ratio“ [AP], 10‘3 M ¢°/¢ 0.0 2.04 3.33 ---- 0.0130 1.86 3.03 1.10 0.0259 1.53 2.49 1.33 0.0389 1.11 1.81 1.84 0.0518 0.983 1.60 2.07 '0.0777 0.700 1.14 2.91 0, 0 pyr 1.41 2.30 ---- “0.044 M ketone; 0.51 M pyridine; RT, 313 nm, 1 hr. b0.11 M VP actinometer: AP/c16 area ratio = 0.786; [C16] = 1.90 x 10"3 M. c[020] = 6.52 x 10‘4 M; column #1, 140°. Run #2: k T = 44 q AP/620 b -3 0 [Q], M Area Ratio [AP], 10 M a la 0.0 0.664 1.20 ---- 0.0056 0.997 1.80 0.67 0.0111 0.802 1.45 0.83 0.0445 0.395 0.713 1.68 0.0667 0.323 0.583 2.06 “0.041 M ketone; 0.50 M pyridine; RT, 313 nm, 40 min. b[czo] = 7.22 x 10‘4 M; column #4, 140°. 204 Table 49. Quenching of p-Carbomethoxyvaler0phenone by Triethyl- amine in Acetonitrile.a Run #1: k T = 93 q AP/c20 b 3 [0], M Area Ratio [AP], 10' M a°la 0.0 1.56 2.70 ---- 0.00701 1.17 2.03 1.34 0.0140 0.848 1.47 1.84 0.0281 0.514 0.891 3.04 0.0561 0.297 0.515 5.25 0.0841 0.194 0.336 8.47 “0.040 M ketone; RT, 313 nm, 25 min. “[020] = 6.93 x 10'4 M; column #1, 138°. Run #2: k a = 91, all = 0.75b q AP/c20 [0], M Area Ratio“ [AP], 10‘3 M a°l¢ 0.0 2.19 3.08 ---- 0.00272 2.12 ‘ 2.98 1.04 0.00545 1.59 2.24 1.38 0.00817 1.46 2.06 1.50 0.0109 1.24 1.75 1.77 0.0163 1.01 1.42 2.16 0.0218 0.815 1.15 2.69 “0.041 M ketone; RT, 313 nm, 30 min. b0.11 M VP actinometer: AP/c16 area ratio = 0.415; [“16] = 1.32 x 10’3 M. I “[020] = 5.63 x 10'4 M; column #1, 140°. '205 Table 49. Continued. . - = b Run #3. qu - 89, all 0.65 AP"320 [0], M Area Ratio“ [AP], 10'3 o°/a 0.0 4.10 5.72 ---- 0 0050 4.20 5.86 0.96 0 0100 3.16 4.41 1.30 0 0200 2.15 3.00 1.91 0.0300 1.57 2.19 2.61 0.0400 1.38 1.93 2.97 0.0600 0.997 1.39 4.11 “0.040 M ketone; RT, 313 nm, 30 min. “0.10 M VP actinometer: AP/cl6 area ratio = 0.329; [“16] = 3.84 -3 x 10 M. “[020] = 5.58 x 10'4 M; column #2, 130°. 206 Table 50. Quenching of m-Divalerylbenzene by Hexadiene in Benzene.a Run #1: k T = 37, all = 0.22b q AP/c24 [0], M Area Ratio“ [AP], 10"3 M a°l¢ 0.0 1.67 3.34 ---- 0.0112 1.08 2.16 1.55 0.0224 0.851 1.70 1.96 0.0448 0.649 1.30 2.57 0.0671 0.464 0.928 3.59 0.0895 0.399 0.798 4.18 0 112 0.348 0.696 4.79 “0.038 M ketone; RT, 313 nm, 1-1/2 hrs. “0.055 M VP actinometer: AP/Cl6 area ratio = 0 904; [cl6] = 2.25 x 10-3 M. 3 “[024] = 1.00 x 10' M; column #4, 195°. Run #2: k T = 38 q AP/c22 [0], M Area Ratio“ [AP], 10'3 M ¢°/¢ 0.0 1.85 2.26 ---- 0.0075 1.45 1.77 1.28 0.0150 1.18 1.44 1.57 0.0300 0.792 0.969 2.34 0.0450 0.765 0.936 2.42 0.0600 . 0.561 0.686 3.30 “0.020 M ketone; RT, 313 nm, 1 hr. “[022] = 6.44 x 10'4 M; column #2, 170°. 207 Table 51. Quenching of 0.032 M m—Divalerylbenzene by Hexadiene in Acetonitrile.a qu . 46. all = 0.70“ AP/C [0], M Area Rgiioc [AP], 10'3 M a°/a 0.0 2.81 3.56 ---- 0.0037 2.50 3.17 1.12 0.0073 2.04 2.59 1.38 0.0146 1.69 2.14 1.67 0 0220 1.38 1.75 2.04 0.0293 1.17 1.48 2.39 0.0439 0.951 1.21 2.96 aRT, 313 nm, 20 min. b0.11 M VP actinometer: AP/c16 area ratio = 0.160; [C16] = 4.55 x 10'3 M. “[czzj = 6.67 x 10"4 M; column #3, 170°. 208 Table 52. Quenching of 0.029 M m-Divalerylbenzene by Triethylamine in Benzene.“ qu = 28, “max = 0.54“ AP/c [Q], M Area REEioc [AP], 10'3 M 40/4 0.0 0.813 2.09 ---- 0 0110 0.754 1.93 1.08 0 0220 0.637 1.63 1.28 0.0440 0.450 1.15 1.81 0.0660 0.340 0.872 2.39 0.0881 0.278 0.713 2.93 0.132 0.204 0.523 3.98 a0.53 M pyridine; RT, 313 nm, 25 min. b0.11 M VP actinometer: AP/C16 area ratio = 0.160; [C16] = 3.49 -3 x 10 M. c[022] = 1.35 x 10'3 M; column #1, 143°. 209 Table 53. Quenching of m-Divalerylbenzene by Triethylamine in Acetonitri1e.a Run #1: k T = 33 q AP/C 22 b -4 o [Q], M Area Ratio [AP], 10 M 4 /4 0.0 0.509 7.41 ---- 0.0050 0.458 6.67 1.11 0.0100 0.383 5.57 1.33 0.0200 0.307 4.47 1.66 0.0300 0.275 4.00 1.85 0.0400 0.214 3.12 2.38 0.0600 0.172 2.50 2.96 “0.037 M ketone; RT, 313 nm, 20 min. b[C22] = 7.66 x 10'4 M; column #2, 152°. Run #2: qu = 34 AP/C 22 b -3 0 [0], M Area Ratio [AP], 10 M 0 Io 0.0 1.15 1.32 ---- 0.0050 1.33 1.53 0.86 0.0100 0.835 0.960 1.38 0.0200 0.672 0.773 1.71 0.0300 0.610 0.701 1.89 0.0400 0.466 0.536 2.47 0.0600 0.396 0.455 2.90 “0.035 M ketone; RT, 313 nm, 25 min. b[C22] = 6.05 x 10'4 M; column #1, 138°. 210 Table 54. Quenching of p-Divalerylbenzene by Hexadiene in Benzene.a Run #1: k T = 188 q AP/Cz4 [0], M Area Ratiob [AP], 10'3 M polo 0.0 1.25 2.27 ---- 0.00401 0.688 1.25 1.82 0.00803 0.504 0.915 2.47 0.0120 0.398 0.723 3.13 0.0161 0.297 0.539 4.20 “0.040 M ketone; RT, 313 nm, 2 hrs. “[c24] = 9.08 x 10'4 M; column #4, 200°. Run #2: k T = 178, a = 0.10b a x = 0.17 q 11 ma AP/c24 [0], M Area Ratio“ [AP],10'3 M a°/a 0.0 1.43 2.47 ---- 0.00417 1.07 1.84 1.34 0.00833 0.623 1.07 2.30 0.0125 0.429 0.740 3.33 0.0167 0.341 0.588 4.19 0, 1 M pyr 2.32 4.00 ---- a0.040 M ketone; RT, 313 nm, 2 hrs. “0.10 M VP actinometer: AP/ch area ratio = 0.845; [C16] = 4.1 x -3 10 M. c[024] = 8.62 x 10'4 M; column #4, 200°. 211 Table 55. Quencging of p-Acetylvalerophenone by Hexadiene in Ben- zene. Run #1: qu . 300, all = 0.10“ AP/c20 [0], M Area Ratio“ [AP], 10"3 M ¢°I4 0.0 1.23 1.79 ---- 0.000622 0.989 1.44 1.24 0.00124 0.819 1.19 1.50 0.00249 0.654 0.952 1.87 0.00373 0.650 0.946 1.89 0.00497 0.527 0.767 2.32 “0.040 M ketone; RT, 313 nm, 2-1/2 hrs. b0.10 M VP actinometer: 'AP/Cle area ratio = 0.848; [C16] = 2.96 -3 x 10 M. c[c201 = 5.60 x 10‘4 M; column #1, 135°. 0 a = b Run #2. qu 400, all 0.09 AP/C20 c -3 0 [Q], M Area Ratio [AP], 10 M a la 0.0 1.73 7.02 ---- 0.000599 1.28 5.19 1.35 0.00120 1.13 4.58 1.53 0.00180 1.01 4.10 1.72 0.00299 0.797 3.23 2.18 “0 032 M ketone; RT, 313 nm, 3 hrs. b0.052 M VP actinometer: AP/c16 area ratio = 1.01; [C16] = 1.94 x -3 10 M. “[020] = 1.56 x 10‘3 M; column #4, 195°. 212 Table 56. Quantum Yields for 0.040 M Trifluoromethylvalerophenones in Benzene.“ AP/C13 or C16 Ketone Area Ratio“ [AP], 10'3 M all“ o-CF3 0.212' 0.382 0.15 o-CF3d 1.22d 2.33 0.89 o-CF3e 1.25e 2.39 0.91 m-CF3 0.224 0.495 0.19 m-CF3d 0.993d 1.89 0.72 m-cr3“ 1.02e 1.95 0.74 p-CF3 0.202 0.611 0.23 p-CF3d 1.26d 2.40 0.92 p-CF3e 1.43e 2.73 1.0 “R1, 313 nm, 30 min. b f0r o-CF VP: [013] = 1.06 x 10 M; for m-CF3VP: [cl3] = 1.30 x 10'3 M; for p-CF3VP: [cl3] = 1.78 x 10'3 M; column #2, 71°. c0.10 M VP actinometer: AP/cl6 area ratio = 0.170; [“16] = 2.21 x 10‘3 M. d 0.050 M pyridine; [016] = 9.54 x 10' e0.10 M pyridine; [“16] = 9.54 x 10'4 M; column #2, 71°. M; column #2, 71°. 213 Table 57. Disappearance Quantum Yields for Cyanovalerophenones in Benzene.“ For m-CNVP: VP/STD b -2 c Area Ratio [VP], 10 M ¢-K Before hv: 1.43 4.35 ---- After hv: 1.31 4.02 0.23 For p-CNVP: VP/STD b -2 c Area Ratio [VP], 10 M °-K Before hv: 1.44 4.13 ---- After hv: 1.32 3.80 0.23 “R1, 313 nm, 4 hrs. 2 “[n-0ctadecy1 benzoate] = 1.67 x 10' M; column #2, 145°. “0.10 M VP actinometer: AP/c16 area ratio = 0.322; [cl5] = 6.31 -3 x 10 M. 214 Table 58. Disappearance Quantum Yields for Cyanovalerophenones in Benzene.“ For o-CNVP: VPNZ“ b -2 a c Area Ratio [VP], 10 M -K Before hv: 2.64 4.97 ---- After hv: 2.45 4.62 0.14 For p-CNVP: VP/C26 d -2 ¢ c Area Ratio [VP], 10 M -K Before hv: 2.58 5.05 ---- After hv: 2.18 4.27 0.31 “R1, 313 nm, 5 hrs. “[026] = 8.07 x 10'3 M; column #2, 165°. c0.10 M VP actinometer: AP/ch area ratio = 0.782; [cl6] = 4.55 x 10'3 M. d [“26] = 8.37 x 10'3 M; column #2, 165°. 215 Table 59. Disappearance Quantum Yields for Cyanovalerophenones in Acetonitri1e.a For o-CNVP: VP/C26 b -2 l c Area Ratio [VP], 10 M -K Before hv: 2.18 5.02 ---- After hv: 1.23 2.83 0.82 For m-CNVP: mm“ b -2 4 C Area Ratio [VP], 10 M -K Before hv: 2.08 4.97 ---- After hv: 1.49 3.56 0.52 For p-CNVP: vp/C26 b -2 a c Area Ratio [VP],10 M -K Before hv: 2.12 5.00 ---- After hv: 1.34 3.17 0.68 “RI, 313 nm, 2-1/2 hrs. “[6261 = c0.10 M VP actinometer: AP/c16 area ratio = 1.36; [“16] = 2.83 x 10‘ 1.02 x 10'2 M; column #2, 165°. 3 216 Table 60. Disappearance Quantum Yields for Carbomethoxyvalerophenones in Acetonitrile.a F0r m-COZCH3VP: VP/C 26 b _2 l c Area Ratio [VP], 10 M -K Befbre hv: 3.13 5.02 ---- After hv: 2.27 3.63 1.0 c Area Ratiob [VP], 10‘2 M “-K Before hv: : 2.98 5.03 ---- After hv: 2.30 3.89 0.83 “R1, 313 nm, 1-1/4 hrs. “[026] = 7.85 x 10'3 M; column #2, 170°. c0.10 M VP actinometer: AP/C16 area ratio = 0.745; [C16] = 2.65 x 10'3M. ‘217 Table 61. Disappearance Quantum Yields for Carbomethoxyvalerophenones in Acetonitri1e.“ For o-COZCH3VP: VP/C 26 b _2 l c Area Ratio [VP], 10 M -K Before hv: 2.43 4.04 ---- After hv: 1.94 3.21 0.25 For m-CDZCH3VP: VP/C26 b -2 9 d Area Ratio [VP], 10 M -K Before hv: 2.06 4.00 ---- After hv: 1.60 3.09 0.85 VP/C26 b -2 ¢ d Area Ratio [VP], 10 M -K Before hv: 2.35 4.07 ---- After hv: 1.85 3.20 0.81 “R1, 313 nm, 4-1/2 hrs for o-CDZGi C020i3VP. “[96] = 8.29 x 10'3 M; column #2, 170°. c0.10 M VP actinometer AP/C16 area ratio 10 M. 3VP, l-1/4 hrs for m- and p- 1.16; [£16] = 4.06 x d 0.10 M VP actinometer: AP/C16 area ratio 0.380; [016] = 4.06 x 10'3 M. 218 Table 62. Maximization 0f oll for 0.040 M p-Cyanovalerophenone by Pyridine in Benzene. all . 0.21b amax - 0.42“ [Pyr], M ' Ar::/:ggioc [AP], 10'3 ¢Ilb 0.0 0.723 .959 0.21 0.075 1.25 .66 0.36 0.30 1.44 .91 0.42 0.45 1.38 .83 0.40 0.60 1.39 84 0.41 0.75 1.30 .72 0.38 1.5 1.12 .49 0.33 3.0 1.34 .78 0.39 “R1, 313 nm, 30 min. b0.10 M VP actinometer: 10'3 M. c - -4 [C20] - 5.1 x 10 11; column #1, 145°. AP/C16 area ratio .167; [C16] = 4.02 x 219 Table 63. Maximization of all for 0.041 M p-Cyanovalerophenone by Dioxane in Benzene.a a - 0.17“ a x = 0.35“ II ma [Dioxane], AP/CZO c _3 4 b M Area Ratio [AP], 10 M II 0.0 0.526 0.755 0.17 1.00 0.975 1.40 0.31 2.01 0.897 1.29, 0.29 3.01 1.06 1.52 0.34 4.02 1.04 1.49 0.33 5.02 1.02 1.46 0.32 6.02 1.01 1.45 0.32 7.03 1.12 1.61 0.36 “RT, 313 nm, 40 min. b0.10 M VP actinometer: AP/Cl6 area ratio = 0.624; [c161 = 1.02 x 10'3 M. “[020] - 5.52 x 10“ M; column #1, 145°. 220 Table 64. Maximization of ¢ll for 0.040 M p-Cyanovalerophenone by t-Butyl Alcohol in Benzene.a all = 0.17b amax = 0.33“ [t-BuOH], AP"320 c _3 a b M Area Ratio [AP], 10 M II 0.0 0.550 1.39 0.17 0.125 0.672 1.69 0.20 0.250 0.731 1.84 0.22 0.375 0.924 2.33 0.28 0.500 0.985 2.48 0.30 0.626 0 991 2.50 0.30 0.751 1.14 2.88 0.35 1.00 1.07 2.70 0.29 “R1, 313 nm, 1 hr, 20 min. b 10'3 M. c _ -4 [C20] - 9.70 x 10 M; column #2, 140°. 0.10 M VP actinometer: AP/C16 area ratio = 0. 603; [C16] = 1.99 x 221 Table 65. Maximization of all for 0.040 M p-Cyanobutyrophenone by Pyridine in Benzene.a all = 0.13“ amax = 0 31“ AP/c20 b [Pyr], M Area Ratio“ [AP], 10'3 M “II 0.0 1.11 1.75 0.13 0.50 2.70 4.29 0.31 1.0 2.97 4.34 0.31 “R1, 313 nm, 1 hr. “0.10 M VP actinometer: AP/ch area ratio = 0.773; [C16] = 2.56 x 10'3 M. 4 “[czo] = 6.36 x 10' M; column #2, 120°. 222 Table 66. Effect of Ketone Concentration on all for p-Carbomethoxy- valerophenone in Acetonitrile.a AP/C [Ketone], 20. b _3 4 c M Area Ratlo [AP], 10 M II 0.020 1.26 2.10 0.47 0.060 1.26 2.10 0.47 0.080 1.34 2.23 0.50 0.10 1.32 2.20 0.49 0.12 1.37 2.28 0.51 0.14 1.34 2.23 0.50 0.16 1.47 2.45 0.55 “RT, 313 nm, 20 min. “[020] = 6.66 x 10“ M; column #3, 165°. c0.10 M VP actinometer: AP/C16 area ratio = 0.691; [C16] = 9.30 x -4 10 M. 223 Table 67. Intersystem Crossing Yield for 0.040 M p-Cyanoacetophenone in Benzene.“ Run #1: °ISC = 1.0 b c d 0.12 (act) 0.0753 1.00 0.12 0.0721 0.96 0.060 (act) 0.136 1.00 0.060 0.143 1.05 a RT, 313 nm, 1 hr. bcis-P = cis 1,3-pentadiene. CB = area trans/area trans + area cis; column #6, 55°. d¢ISC = Bketone/Bact; 0.060 M acetophenone actinomer. Run #2: ¢ISC = 1.0 [cis-P], Mb BC olscd 0.060 (act) 0.0673 1.00 0.060 0.0740 1.10 0.030 (act) 0.118 1.00 0.030 0.129 1.09 0.0050 (act) 0.413 1.00 0.0050 0.404 0.98 “R1, 313 nm 45 min. bcis-P = cis 1,3-pentadiene. c8 = area trans/area trans + area cis; column #6, 55°. d¢ISC = Bketone/Bact; 0.060 M acetophenone actinometer. 224 Table 68. Intersystem Crossing Yield for 0.050 M p-Carbomethoxy- valerophenone in Benzene.“ c d [cis-P], Mb 8 ¢ISC 0.050 (act) 0.204 1.00 0.050 0.201 0.99 0.10 (act) 0.134 1.00 0.10 0.137 1.02 “R1, 313 nm, 2-1/2 hrs. b[cis-P] = cis 1,3-pentadiene. c d 8 = area trans/area trans + area cis; column #6, 55°. ¢ISC = Bketone/Bact; 0.050 M valerophenone actinometer. 225 Table 69. Quenching of 0.050 M p-Cyanoacetophenone by Naphthalene in Acetonitri1e (1.0 M Toluene).“ k1322X1& q 88/621 -4 b -3 c 0 [Q], 10 M Area Ratio [88], 10 M a [a 0.0 1.58 2.16 ---- 0.501 0.712 0.972 2.21 1.00 0.489 0.668 3.22 1.50 0.376 0.513 4.19 “R1, 366 nm, 13 hrs. “88 = bibenzyl; [“21] = 9.10 x 10'4 M; column #2, 130°. cReSponse factor for C21/BB = 1.5. 226 Table 70. Photoreduction of 0.051 M p-Cyanoacetophenone by Tbluene in Acetonitrile.“ Slope = 18.8, intercept = 1.8 557:5“ b -3 c -2d [Toluene], M Area Ratio [88], 10 M 938, 10 0.250 0.234 0.351 0.996 0.500 0.476 0.714 2.02 0.625 0.646 0.969 2.74 0.750 0.718 1.08 3.13 0.875 0.831 ' 1.25 3.53 1.00 0.850 1.28 3.61 1.25 1.10 1.65 4.67 “R1, 313 nm, 3 hrs. “88 = bibenzyl; [“21] = 1.00 x 10"3 M; column #2, 120°. cResponse factor for C21/BB = 1.5. d0.10 M VP actinometer: AP/c16 area ratio = 1.25; [C16] = 4.02 x 10'3 M. 227 Table 71. Quenching of 0.050 M p-Cyanoacetophenone by Naphthalene in Dry Acetonitri1e (1.0 M p-Xylene).a qu = 4,750 p-dilE/c16 [0], 10‘3 M Area Ratio“ [p-diTE], 10‘3 M“ a°/a 0.0 1.54 3.10 ---- 0.501 0.507 1.02 3.04 0.751 0.390 0.784 3.95 1.00 0.282 0 567 A 5.46 1.25 0.204 0.410 7.56 1.50 0 178 0.358 8.65 “R1, 366 nm, 7-1/2 hrs. “p-dilE = p-ditolylethane; [“16] = 2.01 x 10‘3 M; column #5, 140°. cResponse factor for Cl6/p-diTE = 1.0. 228 Table 72. Photoreduction of 0.050 M p-Cyanoacetophenone by p- Xylene in Dry Acetonitrile.“ Slope = 1.7, intercept = 8.5 [p-Xylene], M Area Ratiob [p-diTE], 10'4 M 433, 10'1 0.313 0.248 5.01 0.733 0.625 0.279 5.64 0.824 0.938 0.319 6.44 0.942 1.25 0.352 7.11 1.04- 1.56 0.367 7.41 1.08 1.88 0.360 7.27 1.06 2.19 0.377 7.62 1.11 “R1, 313 nm, 30 min. b p-diTE = p-ditolylethane; [C16] = 2.02 x 10' 3 cResponse factor for Cl6/p-diTE = 1.0. M; column #5, 140°. d0.10 M VP actinometer: AP/C16 area ratio = 0.215; [Cls] = 4.55 x 10'3 M. ‘ 229 Table 73. Quenching of 0.040 M p-Carbomethoxyvalerophenone by B-Dimethylaminoethyl Benzoate in Benzene.“ kqt = 32, all e 0 29“ AP/c [0], M Area Ritioc [AP], 10'3 M a°la 0.0 0.897 3.13 ---- 0.0300 1.07 3.73 0.84 0.0600 0.795 2.77 1.13 0.120 0.473 1.65 1.90 0.180 0.328 1.14 2.74 0.240 0.247 0.861 3.62 “0.50 M pyridine; RT, 313 nm, 30 min. b0.10 M VP actinometer: AP/c16 area ratio = 0.667; [C16] = 2.34 x 10'3 M. “[Cle = 1.34 x 10'3 M; column #2, 131°. 230 Table 74. Quenching of p-Carbomethoxyvalerophenone by B-Dimethyl- aminoethyl Benzoate in Acetonitri1e.“ Run #1: qu = 40, all = 0.55“ AP/c20 [0], M Area Ratio“ [AP], 10‘3 M 4°la 0.0 1.24 1.80 ---- 0.00250 1.74 2.52 0.71 0.0050 1.58 2.29 0.79 0 0100 1.36 1.97 0.91 0.0150 1.41 2.04 0.88 0 0200 1.17 1.70 1.06 “RT, 313 nm, 25 min. b 0.10 M VP actinometer: AP/Cl6 area ratio -3 10 M. c[020] = 5.80 x 10'4 M; column #3, 161°. 0.169; [C16] = 2. Run #2: k T 8 40 q AP/c20 [0], M Area Ratio“ [AP], 10‘3 M a°/a 0.0 2.83 4.05 ---- 0 0125 3.43 4.90 0.83 0.0250 2.95 4.22 0.96 0.0500 1.90 2.72 1.49 0.0750 1.42 2.03 2.00 “R1, 313 nm, 30 min. “[020] = 5.72 x 10‘4 M; column #3, 161°. 231 Table 75. Quenching of 0.040 M p-Carbomethoxyvalerophenone by y-Dimethylaminopropyl Benzoate in Benzene.“ qu = 26, amax = 0.33“ AP/CZO [0], M Area Ratio“ [AP], 10'3 M a°/¢ 0.0 1.31 2.32 ---- 0.0250 1.35 2.39 0.97 0.0500 0.958 1.70 1.37 0 100 0.619 1.10 2.12 “0 50 M pyridine; RT, 313 nm, 40 min. b0.10 M VP actinometer: AP/C16 area ratio = 0.307; [Cl6] = 3.31 -3 x 10 M. “[020] = 7.08 x 10’4 M; column #3, 170°. 232 Table 76. Quenching of 0.040 M p-Carbomethoxyvalerophenone by y-Dimethylaminopropyl Benzoate in Acetonitrile.“ 8 8 b k T 47, all 0.50 q AP/c20 [0], M Area Ratio“ [AP], 10‘3 M a°/a 0.0 2.52 3.56 ---- 0.0125 2.65 3.74 0.95 0.0250 1.96 2.77 1.29 0.0500 1.26 1.78 2.00 0.0750 0.962 1.36 2.62 0.100 0.732 1.03 3.45 aRT, 313 nm, 40 min. “0.10 M VP actinometer: AP/c16 area ratio = 0.881; [C16] = 1.19 -3 x 10 M. “[020] = 5.65 x 10'4 M; column #3, 170°. 233 Table 77. Quenching of 0.040 M m-Carbomethoxyvalerophenone by B-Dimethylaminoethyl Benzoate in Acetonitri1e.“ qu = 8.0 AP/CZl b -3 [Q], M Area Ratio [AP], 10 M ¢°/¢ 0.0 3.15 7.21 ---- 0 0100 3.35 7.66 0.94 0.0200 3.12 7.14 ' 1.01 0.0300 2.83 6.48 1.11 0.0400 2.64 6.04 1.19 0.0600 2.45 5.61 1.28 0 0800 2.18 4.99 1.44 “R1, 313 nm, 20 min. b[CZl] = 8.80 x 10'4 M; column #2, 130°. 234 Table 78. Quenching of p-Methoxyvalerophenone by Pentadiene in Benzene. Run #1: k t = 4,860, all = 0.11“ q AP/c22 [0], 10‘3 M Area Ratio“ [AP], 10'3 M a°la 0.0 0.740 1.00 ---- . 0 125 0.460 0.624 1.61 0.250 0.305 0 413 2.43 0 500 0.231 0 313 3.20 0 750 0.152 0.206 4.87 1.00 0.136 0.184 5.45 a0.040 M ketone; RT, 313 nm, 1 hr, 20 min. b0.10 M VP actinometer: AP/c16 area ratio = 0.512; [C16] = 2.52 x 10‘3 M. “[022] = 5.02 x 10" M; column #2, 130°. Run #2: qu = 3750 AP/c22 [0], 10‘3 M Area Ratio“ [AP], 10'3 M ¢°/¢ 0.0 1.58 2.80 ---- 0.125 0.964 1.71 1.64 0.250 0.894 1.58 1.77 0.500 0.697 1.23 2.27 0.750 0.433 0.767 3.65 1.00 0 360 0.638 4.40 1.50 0.241 0.427 6.56 “0.040 M ketone; RT, 313 nm, 2 hrs. b[sz] = 6.56 x 10"4 M; column #2, 145°. 235 Table 79. Quenching of p-Methoxyvalerophenone by Pentadiene in Aceto- nitrile.“ Run #1: k a = 6,800, all = 0 21“ q AP/c20 [0], 10’4 M Area Ratio“ [AP], 10'3 M a°/a 0.0 1.11 2.80 ---- 1.00 0.672 1.70 1.70 2.00 0.468 1.18 2.45 4.00 0 307 0.775 3.73 6.00 0.228 0.576 5.04 “0.040 M ketone; RT, 313 nm, 6-1/2 hrs. b0.10 M VP actinometer: AP/C16 area ratio x 10'3 M. c[C20] = 1.01 x 10‘3 M; column #2, 140°. 0.276; [C16] = 2.61 Run #2: k T = 6,000 q AP/c22 [0], 10'4 M Area Ratio“ [AP], 10‘3 M a°la 0.0 0.515 2.81 ---- 0 500 0.410 2.24 1.25 1.00 '0.324 1.77 1.59 2.00 0.228 1.24 2.26 3.00 0.193 1.05 2.67 4.01 0.147 0.802 3.54 6.01 0.111 0.605 4.64 “0.040 M ketone; RT, 313 nm, 1-1/2 hrs. b[022] = 2.02 x 10'3 M; column #2, 140°. 236 Table 80. Quenching of 0.040 M p-Methoxyvalerophenone by N,N- Dimethylaminopropyl Phenyl Ether in Acetonitrile.“ qu = 202 AP/c22 [0], 10'2 M Area Ratio“ [AP], 10'4 M a°/a 0.0 0.936 8.69 ---- 0.400 0.944 8.77 0.99 0.801 0.656 6.09 1.43 1.60 0.435 4.04 2.15 2.40 0.293 2.72 3.20 3.20 0.233 2.16 4.03 “R1, 313 nm, 40 min. “[022] = 3.44 x 10“ M; column #2, 140°. 237 Table 81. Quenching of 0.020 M p-ZVB by Pentadiene in Benzene.“ qu = 9.4 all = 0.068“ ”/6 [Q], M Area Rgfiioc [AP], 10'4 M ¢°/0 0.0 0.877 8.07 ---- 0.0125 0.819 7.54 1.07 0.0250 0 767 7.06 1.14 I 0.0500 0.690 6.35 1.27 0 0750 0.590 5.43 1.49 0.100 0.520 4.78 1.69 0.150 0.424 3.90 2.07 “0.40 M pyridine; RT, 313 nm, 2 hrs. “0.11 M VP actinometer: AP/ch area ratio = 0.476; [C16] = 3.58 x -3 10 M. “[024] = 4.60 x 10‘4 M;co1umn #2, 170°. 238 Table 82. Quenching of 0.030 M p-2VB by Pentadiene in Benzene.a k a = 10.1, all = 0.077“ q AP/c24 [q], M Area Ratio“ [AP], 10‘4 M a°/4 0.0 0.729 8.78 ---- 0.0125 0.684 8.24 1.07 0.0250 0.639 7.69 1.14 0.0500 0.567 ' 6.83 1.29 0.0750 0.485 - 5.84 1.50 0 100 0.432 5.20 1.69 0 150 0.327 3.94 2.23 “0.40 M pyridine; RT, 313 nm, 2-1/4 hrs. “0 10 M VP actinometer: AP/c16 area ratio = 0.552; [C16] = 2.96 x -3 10 M. c[c24] = 6.02 x 10’4 M; column #2, 170°. 239 Table 83. Quenching of 0.040 M p-2VB by Pentadiene in Benzene. k r = 10.6, all = 0.079“ q AP/c24 [0], M Area Ratio“ [AP], 10‘4 M a°/a 0.0 0.649 8.59 ---- 0.0150 0.602 7.97 1.08 0.0300 0 562 7.44 1.15 0 0600 0.451 5.97 1.44 0.0900 0.396 5.24 1.64 0 120 0.335 4.44 1.94 0.180 0.249 3.30 - 2.61 “0.40 M pyridine; RT, 313 nm, 2-1/2 hrs. b0.10 M VP actinometer: AP/C16 area ratio = 0.452; [C 3.44 x 10.3 M. 16] = “[024] = 6.62 x 10"4 M; column #2, 170°. 240 Table 84. Quenching of 0.010 M p-2VB with Pentadiene in Acetonitri1e.a qu = 13.6, all = 0.10“ AP/STD [Q], M Area Ratioc [AP], 10'4 M ¢°I¢ 0.0 0.849 6.58 ---- 0 0125 0.828 6.42 1.16 0.0250 0.807 6.25 1.32 0.0500 0.713 5.53 1.62 0 0750 0.628 4.87 2.10 0 100 0.510 3.95 2.33 0.150 0.395 3.06 3.02 aRT, 313 nm, 30 min. “0.10 M VP actinometer: AP/Cl6 area ratio = 0.609; [“16] = 1.46 x 10'3 M. “[n-0ctadecy1 benzoate] = 3.10 x 10'4 M; column #2, 170°. '241 Table 85. Quenching of 0.020 M p-2VB by Pentadiene in Acetonitrile.a kqt = 12.3, all = 0.11“ AP/STD [0], M Area Ratio“ [AP], 10‘3 M a°/a 0.0 1.46 1.33 ---- 0.0125 1.19 1.08 1.22 0.0250 1.08 0.983 1.35 0.0500 0.860 0.783 1.70 0.0750 0.809 0.736 1.81 0 100 0.691 0.629 2.11 0.150 0.522 0.475 2.80 “R1, 313 nm, 1 hr. “0.10 M VP actinometer: AP/cl6 area ratio = 0.565; [C16] = 3.09 x 10"3 M. 4 c[n-Octadecyl benzoate] = 3.64 x 10' M; column #2, 170°. 242 Table 86. Quenching of 0.040 M p-ZVB by Pentadiene in Acetonitrile.a qu = 10.6, all = 0.11“ AP/STD [0], M Area Ratio“ [AP], 10'3 M a°la 0.0 1.03 1.97 ---- 0.0125 0.982 1.88 1.05 0.0250 0.936 1.79 1.10 0.0501 0.633 1.21 1.63 0.0751 0.572 1.09 1.80 0 100 0.501 0.957 2.05 0.150 0.378 0.722 2.72 “R1, 313 nm, 2-1/2 hrs. b0.10 M VP actinometer: AP/C16 area ratio = 0.561; [cl6] = 4.37 x -3 10 M. 4 c[n-Octadecyl benzoate] = 7.64 x 10’ M; column #2, 170°. 243 Table 87. Quenching of 0.060 M p-2VB of Pentadiene in Acetonitri1e.“ L qu = 8.6, all = 0.097“ AP/STD [0], M Area Ratio“ [AP], 10"3 M a°/a 0.0 0.628 1.79 ---- 0.0125 0.557 1.59 1.13 0 0251 0.540 1.54 1.16 0.0501 0 465 1.33 1.35 0.0752 0.399 1.14 1.57 0.100 0.338 0 963 1.86 0.150 0.244 0.695 2.57 “RT, 313 nm, 3 hrs. “0 10 M VP actinometer: AP/c16 area ratio = 0.908; [C16] = 3.00 x 10‘3 M. c[n-Octadicyl benzoate] = 1.14 x 10'3 M; column #2, 170°. 244 Table 88. Quenching of 0.080 M p-2VB by Pentadiene in Acetonitri1e.a qu = 7.5, all = 0.068“ AP/STD [0], M Area Ratio“ [AP], 10'3 M a°/a 0.0 1.23 2.32 ---- 0 0125 1.09 2.05 1.13 0.0250 1.07 2.02 1.15 0.0500 0.868 1.64 1.42 0 0750 0.804 1.52 1.53 0.100 0.695 1.31 1.77 0.150 0.589 1.11 2.09 “RT, 313 nm. 2-1/2 hrs. “0 10 M VP actinometer: AP/c16 area ratio = 1.53; [clfi] = 3.18 x -3 10 M. c[n-Octadecyl benzoate] = 7.54 x 10"3 M; column #2, 170°. 245 Table 89. Quenching of 0.10 M p-2VB by Pentadiene in Acetonitri1e.“ kqt = 7.3, all = 0.078“ AP/STD [Q], M Area Ratio“ [AP], 10'3 M a°la 0.0 0.748 1.93 ---- 0 0125 0.744 1.92 1.01 0 0250 0 658 1.69 1.14 0.0500 0.542 1.40 1.38 0.0750 0.481 1.24 1.56 0.100 0 410 1.06 1.82 0.150 0.366 0.943 2.04 “RT, 313 nm, 2-1/2 hrs. “0.10 M VP actinometer: AP/c16 area ratio = 0.930; [C16] = 3.84 x 10‘3 M. c[n-Octadecyl benzoate] = 1.03 x 10'3 M; column #2, 170°. 246 Table 90. Quenching of 0.020 M p-3VB by Pentadiene in Acetonitrile.a 4 qu = 11.4, all = 0.13“ AP/STD [0], M Area Ratio“ [AP], 10'3 M a°/a 0.0 1.57 1.51 ---- 0 0125 1.33 1.28 1.18 0.0250 1.22 1.17 1.29 0 0500 0.970 0.931 1.62 0.0750 0.848 0.814 1.85 0.100 0 707 0.679 2.22 0.150 0.611 0.587 2.57 “RT. 313 nm. 1 hr. “0 10 M VP actinometer: AP/cl6 area ratio = 1.07; [C16] = 1.46 x 10'3 M. c[n-Dctadecyl benzoate] = 3.84 x 10’4 M; column #2, 170°. 247 Table 91. Quenching of 0.040 M p-3VB by Pentadiene in Acetonitri1e.“ qu = 7.8, all = 0.093“ AP/STD [Q], M Area Ratio“ [AP], 10‘3 M a°la 0.0 1.10 2.04 ---- 0.0125 1.04 1.93 1.06 0.0250 0.911 1.69 1.20 0 0500 0.790 1.47 1.39 0.0750 0 701 1.30 1.57 0 100 0 600 1.11 1.83 0.150 0.497 0.922 2.21 “RT, 313 nm, 2 hrs. “0.10 M VP actinometer: AP/Cl6 area ratio = 0.879; [“16] = 3.44 x 10‘3 M. 4 “[n-0ctadecy1 benzoate] = 7.42 x 10' M; column #2, 170°. 248 Table 92. Quenching of 0.060 M p-3VB by Pentadiene in Acetonitri1e.“ kqt = 7.5, all a 0.071“ AP/STD [0], M Area Ratioc [AP], 10'3 M ¢°/¢ 0.0 0.855 1.84 ---- 0.0125 0.817 1.76 1.05 0.0250 0.720 1.55 1.19 0 0500 0 578 1.24 1.48 0 0750 0.598 1.29 1.43 0 100 0.479 1.03 1.79 0.150 0.400 0.860 2.14 “RT, 313 nm, 2 hrs. “0.10 M VP actinometer: AP/cl6 area ratio = 1.70; [“16] = 2.08 x -3 10 M. c[n-Octadecyl benzoate] 8 8.60 x 10'4 M; column #2, 170°. 249 Table 93. Quenching of 0.10 M p-3VB by Pentadiene in Acetonitrile.a 3 _ b k T 6.49 ¢II ' 0.082 q AP/STD [Q], M Area Ratio“ [AP], 10'3 M a°la 0.0 0.905 2.51 ---- 0.0125 0.888 2.46 1.02 0.0250 0.787 2.18 1.15 ‘ 0.0500 0 684 1.90 1.32 0.0750 0.598 1.66 1.51 0 100 0.551 1.53 1.64 0.150 0.466 1.29 1.94 “RT, 313 nm, 3 hrs, 40 min. “0.10 M VP actinometer: AP/c16 area ratio = 2.21; [C16] = 1.90 x 10‘ M. “[n-0ctadecy1 benzoate] = 1.11 x 10'3 M; column #2, 170°. 250 Table 94. Quenching of 0.020 M m-2VB by Pentadiene in Benzene.a qu = 15, all = 0 15“ AP/STD [Q], M Area Ratio“ [AP], 10"3 M a°la 0.0 1.41 1.40 ---- 0.0125 1.20 1.19 1.17 0.0250 1.07 1.06 1.32 0.0500 0.850 0.842 1.66 0 0750 0 701 0.694 2.01 0.100 0.578 0 572 2.44 0.150 0.415 0.411 3.40 “RT, 313 nm, 50 min. b0.10 M VP actinometer: AP/cl6 area ratio = 0.588; [C16] = 2.30 x 10’ M. 4 “[n-octadecyl benzoate] = 3.96 x 10' M; column #2, 170°. 251 Table 95. Quenching of m-2VB by Pentadiene in Acetonitri1e.a Run #1: kqt = 24, all = 0.31b AP/STD [Q], M Area Ratioc [AP], 10'3 M ¢°/¢ 0.0 0.944 1.06 ---- 0.0125 0.704 0.789 1.34 0.0250 0.583 0.653 1.62 0.0500 0.426 0.477 2.22 0.0750 0.345 0.386 2.73 0:100 0.285 0.319 3.31 0.150 0.199 0.223 4.75 “0.020 M ketone; RT, 313 nm, 35 min. “0.10 M VP actinometer: AP/Cl6 area ratio = 0.172; [“16] = 3.44 x 10 c[n-Dctadecyl benzoate] = 4.48 x 10'4 M; column #2, 170°. -3 Run #2: qu = 22, all = 0.31“ AP/STD [Q], M Area Ratio“ [AP], 10'3 M a°/a 0.0 2.04 1.96 ---- 0.0125 1.62 1.56 1.23 0 0250 1.36 1.31 1.46 0.0500 1.05 1.01 1.91 0.0750 0.851 0.817 2.34 0 100 0.691 0.663 2.95 0.150 0.535 0.514 3.81 “0.020 M ketone; RT, 313 nm, 30 min. 0.10 M VP actinometer: AP/cl6 area ratio = 0.674; [“16] = 1.37 x 10'3 M. c[n-Dctadecyl Benzoate] = 3.84 x 10'4 M; column #2, 170°. b 252 Table 96. Effect of Ketone Concentration on all for p-ZVB and p-3VB in Acetonitrile.“ For p-2VB: “a = 0 13“ For p-3VB: a” = 0.11b AP/STD [p-2VB], M Area Ratio“ [AP], 10'3 M all“ 0.020 1.56 1.93 0.10 0.040 1.49 1.84 0.098 0 060 1.23 1.52 0.081 0.080 1.18 1.46 0.078 0.120 1.05 1.30 0.069 4 ~ AP/STD -3 c [p 3VBJ’ M Area Ratioc [AP]’ 10 M ¢II 0.020 1.46 1.73 0.092 0 040 1.56 1.86 0.099 0.060 » 1.51 1.79 0.095 0.080 1.41 1.68 ' 0.090 0.120 1.33 . 1.59 0.085 “RT, 313 nm, 1-1/2 hrs. . b0.10 M VP actinometer: AP/Cl6 area ratio = 1.69; [Cl6] = 1.59 x 10'3 M. c[n-Octadecyl benzoate] = 4.95 x 10'4 M; column #2, 170°. ' 253 Table 97. Disappearance Quantum Yields for p-2VB and p-2AB in Aceto- nitrile.a Run #1: For p-2VB: VP/STD b _2 c Area Ratio [VP], 10 M a_K Before hv: 1.60 4.00 ---- After hv: 1.24 3.11 0.39 For p-ZAB: AP/STD b _2 c Area Ratio [AP], 10 M a_K Before hv: 1.34 4.06 ---- After hv: 1.02 3.08 0.43 “RT. 313 nm. 4 hrs. b[n-Octadecyl benzoate] = 1.20 x 10'2 M; column #2, 170°. c0.10 M VP actinometer: AP/Cl6 area ratio = 0.852;[C16] = 3.89 x 10"3 M. Run #2: For p-2VB: VP/STD b -1 a c Area Ratio [VP], 10 M -K Before hv: 3.63 1.00 ---- After hv: 1.55 0.426 0.50 aRT, 313 nm, 6 hrs. “[n-0ctadecy1 benzoate] = 2.02 x 10'2 M; column #2, 170°. “0 10 M VP actinometer: AP/Cl6 area ratio = 4.87; [C16] = 3.36 x 10'3 M. 254 Table 97. Continued. p-ZAB: AP/STD c Area Ratio“ [AP], 10‘2 M “-K Before hv: 3.00 2.00 ---- After hv: 1.45 0.967 0.20 “RT, 313 nm. 3 hrs. b[n-Octadecyl benzoate] = 4.04 x 10"3 M; column #2, 170°. c0.10 M VP actinometer: AP/C16 area ratio = 2.21; [Cl6] = 3.36 x 10"3 M. Run #3: For p-ZVB: VP/STD b _3 l c Area Ratio [VP], 10 M -K Before hv: 2.63 5.08 ---- After hv: 1.48 2.85 0.23 Since only 78% of ho was absorbed, then a_K = 0.29. For p-2AB: AP/STD b _3 l c Area Ratio [AP], 10 M -K Before hv: 1.82 5.06 ---- After hv: . 1.60 4.46 0.06 Since only 89% of ho was absorbed, then a_K = 0.07 “RT, 313 nm, 40 min. “[n-octadecyl benzoate] = 1.36 x 10‘3 M; column #2, 170°. “0.10 M VP actinometer: AP/c16 area ratio = 0.886; [C16] = 1.55 x 10'3 M. 255 Table 98. Quenching of 0.020 M p-Me03E by Pentadiene in Acetonitri1e.a L kqt= 3.6 all = 0.030“ AP/c22 [Q], M Area Ratio“ [AP], 10'3 M a°/a 0.0 1.11 1.29 ---- 0 0200 0.617 0.718 1.80 0.0399 0.425 0.495 2.61 0.0599 0.354 0.412 3.13 0.0799 0.291 0.339 3.81 1.20 0.199 0.232 5.59 1.60 0.219 0.255 5.06 2.16 0.139 0.162 7.99 “RT, 313 nm, 2-1/2 hrs. “0.10 M VP actinometer: AP/cl6 area ratio = 1 20; [“16] = 5.21 x 10"3 M. “[022] = 4.31 x 10’4 M; column #2, 165°. 256 Table 99. Quenching of p-3VE by Pentadiene in Benzene.a Run #1: k a . 2,900, a x = 0 22“ q ma AP/c24 [Q], 10"3 M Area Ratio“ [AP], 10’3 M ¢°/¢ 0.0 1.88 2.10 ---- 0.100 1.47 1.64 1.28 0.200 1.23 1.37 1.53 0.400 0.877 0.979 2.14 0.600 0.691 0.771 2.72 1.20 0.408 0 455 4.61 “0 020 M ketone; 0.50 M pyridine; RT, 313 nm, 1 hr. b0.10 M VP actinometer: AP/Cl6 area ratio = 0 433; [“16] = 3.09 x 10"3 M. “[024] = 4.75 x 10‘4 M; column #2, 165°. Run #2: qu = 3,025, all = 0.07“ AP/c24 [Q], 10'3 M Area Ratio“ [AP], 10'4 M a°la 0.0 0.761 7.08 ---- 0.100 0.615 5.72 1.24 0 200 0.491 4.57 1.55 0.400 0.343 3.19 2.22 0.600 0.259 2.41 2.94 0.800 0 234 2.18 3.25 1.12 0.160 1.49 4.76 “0 020 M ketone; RT, 313 nm, 1-1/2 hrs. b0.099 M VP actinometer: AP/Cl6 area ratio = 0.621; [C16] = 2.21 x 10’3 M. “[024] = 3.96 x 10'4 M; column #2, 165°. 257 Table 100. Quenching of Ketone Disappearance for p-3VE and p-2AE by Pentadiene in Acetonitri1e.“ For p-3VE: k T = 122 q VP/c26 [Q], 10‘2 M Area Ratio“ [VP], 10'2 M Before hv: 0.0 2.39 2.00 After hv: 0.0 1.18 0.989 After hv: 1.25 1.91 1.60 “RT, 313 nm. 3 hrs. “[026] = 5.24 x 10"3 M; column #2, 150°. For p-3AE; -k T = 176 q AP/C24 [Q], 10'2 M Area Ratiob [AP], 10'2 M Before hv: 0.0 1.29 2.00 After hv: 0.0 0.61 0.952 After hv: 1.25 1.07 1.67 “RT, 313 nm, 3 hrs. “[024] = 6.67 x 10"3 M; column #2, 150°. 258 Table 101. Phosphorescence Lifetime for 1.0 x 10'4 M m-Carbomethoxy- benzophenone and arel for 1.0 x 10" M m-288 in 0014.“ kqt . 2.3 x 105 For m-COZCH3BP: [Diene], 10'6 M“ I I°/I 0.0 60 ---- 2.0 43 1.40 4.0 36 1.67 6.0 26 2.31 8.0 18 3.33 For m-COZCH3BP: [Amine], 10'4 M“ I I°/I 1.0 30 2.0 For m-ZBB: [01. M I 0.0 6.5 3RT, 290 nm, monitor at 426 nm. “Diene = 2,5-dimethy1hexa-2,4-diene. cAmine = N,N-dimethylaminoethylbenzoate. 259 Table 102. Phosphorescence Lifetime for 1.0 x 10'4 M p-Carbomethoxy- benzophenone and ¢re1 for 1.0 x 10"4 M p-ZBB in CClll.a th = 5.3 x 105 For p-C02CH3BP: [Diene], 10'“ M“ I I°/I 0.0 574 ---- 4.0 192 3.0 8.0 106 5.4 For p-COZCH3BPz. [Amine], 10'4 M“ I I°/I 1.0 433 1.3 For p-2BB [0]. M I 0.0 51 “RT, 290 nm, monitor at 437 nm. “Diene = 2,5-dimethy1hexa-2,4-diene. cAmine = N,N-dimethylaminoethylbenzoate. 260 4 Table 103. Phosphorescence Lifetime for 1.0 x 10' M p-ZBB in CC14. Run #1: qu = 2.6 x 104 [Diene], 10‘4 M“ I I°/I 0.0 127 ---- 0.8 77 1.65 1.2 22 5.8 1.6 25 5.1 aRT, 300 nm, monitor at 440 nm. bDiene = 2,5-dimethy1hexa-2,4-diene. Run #2: kq = 4.2 x 104 [Diene], 10'5 M“ I I°/I 0.0 44 ---- 0.4 43 1.02 2.0 39 1.13 4.0 18 2.44 8.0 9 4.89 “RT, 290 nm, monitor at 475 nm. “Diene = 2.5-dimethy1hexa-2,4-diene. 261 Table 104. Quenching of 0 040 M Butyrophenone in 0014.“ - a b qu - 710, ¢II 0.34 AP/C -3 ‘5 c -3 [Diene], 10 M Area Ratio [AP], 10 M ¢°I¢ 0.0 . 1.80 1.16 ---- 2.02 0.698 0.452 2.57 4.04 0.449 0.291 4.01 6.06 0.363 0.235 4.95 3RT, 313 nm, 40 min. b0.10 M VP actinometer: AP/c16 area ratio = 0.228; [“16] = 2.16 x 10 4 c[°15] = 3.01 x 10' M; column #3, 125°. kqt = 280 -3 AP/c‘“ b -3 [Et3N], 10 M Area Ratio [AP], 10 M a°la 0.0 1.80 1.16 ---- 1.00 1.67 1.08 1.08 2.00 1.44 0.932 1.25 3.00 1.12 0.725 1.61 4.00 0.757 0.490 2.37 “RT, 313 nm, 40 min. 4 b[C15] = 3.01 x 10' M; column #3, 125°. (JON 10. 11. 12. REFERENCES A. Jablonski, Z. Physik, 24, 38 (1935). E. F. Ullman, Accts. Chem. Res., A, 353 (1968). N. J. Turro, "Molecular Photochemistry“, N. A. Benjamin, Inc., N New York, 1967, Chapter 4. (a) M. A. El-Sayed, Accts. Chem. Res., ;, 8 (1968). (b) 1. M.)Rentzepis and G. E. Busch, M01. Photochem., 4, 353 1972 . 7 (c) R. M. Hochstrasser, H. Lutz and G. N. Scott, Chem. Phys. Lett. , 24,162 (1974). R. M. 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