QUENCE-flNG STUDIES 'ON THE PHOTOCHEMICAL REARRANGEMENT or: CYCLIC KETONES THESIS FOR THE DEGREE OF M. S. MICHIGAN SIATE mm ROGER WILLIAM SPOERKE I 9 6 9 _. __ ”t, v—m «In- - _ T) Li J. V‘: 37 NdlLl h; in \ "(C lJnivcrmty “.— TH ESIS ’h. .T..__. ' I — 0%.— “1:1. - .. “T: “1": "P" co-oa'hsa ‘qu ;;"' flflmfi-Mi .8 I This is to certify that the thesis entitled ‘ aim/w g‘fmJ/éé cw fie x FMEMf 0%l {WWC’fOC/qé’yn ma / fiflfik’flfl/GF . (yd/xc ,[2774M3' i presented by ‘ Veg 56 M ///W Ska WK E: \ has been accepted towards fulfillment of the requirements for Ldegree in____._.__ CLFW/fé/f pflufiiw i VMa r profesun 0-169 , ' ' '- Quenching Studies on the Photochemical Rearrangement of Cyclic Ketones BY Roger Wm. Spoerke A 'I'nesis Submitted to Michigan State University in partial fulfillment of the requirements for the degree of Master of Science Department of Chemistry 1969 Acknowledgements I am.indeed grateful to Dr. Peter J. Wagner for providing his excellent counsel and facilities throughout this investigation and for his financial assistance during the summers of 1966 and 1967. Regarding advice on purely scientific matters, I am indeed indebted to many of my collegues at Michigan State University for the many lively and useful discussions during the course of this work and for the interest they have shown throughout. Lastly,it is my pleasure to thank my wife not only for her assistance in preparing this manuscript but also for her sympathetic encouragement during those early dark days when results were few and prag- ress seemed negligible. ii Abstract Dienes were used to quench the photoisomer- ization of several cycloalkanones in dilute solution. Cyclopentanone and substituted cyclohexanones apparantly undergo the photoisomeric reaction via the triplet excited state, in the liquid phase. Rate constants were calculated for these various ketones in their triplet states: cyclopentanone, 1.1 x 108 sec‘l; cyclohexanone, 3.3 x 107sec'1; 2-methylcyclo- hexanone, 4.7 x 1083ec'1; 3-methylcyclohexanone, 2.5 x 107 7 1 sec'l; 3,S-dimethylcycIOhexanone, 2.4 x 10 sec" ; 3,3,5- 7sec'l; 2,6-dimethy1- trimethylcyclohexanone, 2.5 x 10 cyclohexanone, 9.3 x 108sec'1; 2—phenylcyclohexanone, 3.3 x 103sec‘1; 2,2-dimethylcyclohexanone, 1.8 x logsec’l. Quantum yields for the disappearance of the ketones and quantum yields for the appearance of their respective triplet products were also determined: cyclopentanone, ¢_k= .27, ¢+p= .24; cyclohexanone, ¢_k=.13, ¢+p= .09; 2amethylcyclohexanone, ¢-k= .50, ¢+p= .42; 3-methylcyclohexanone, ¢_k= .08, ¢+p= .03; 3,5-dimethyl- cyclohexanone, ¢_k= .03, flip: .005; 2,6-dimethylcyclo- hexanone. {5-15 .56, ¢+p= .40; 3,3,5-trimethylcyclo- hexanone, ¢~k= .02, ¢+p= .002; 2-phenylcyclohexanone, iii ¢_k= .51, ¢+p= .04; 2,2-dimethylcyclohexanone, ¢;k= .54, ¢+p= «42. It is proposed that reactivities of n;fl$ carbonyl triplets are dependant on ring size and sub- stitution on the ring. Table of Contents Page Acknowledgements..................................... ii Abstract............................................. iii List of Figures...................................... vii List of Tables....................................... ix Introduction......................................... 1 Results.............................................. 12 Quenching Studies Cyc10pentanone.................................... 14 Cyclohexanone..................................... 14 2amethylcyclohexanone............................. 14 3-methylcyclohexanone............................. 15 3,S-dimethylcyclohexanone......................... 15 3,3,5-trimethylcyclohexanone...................... 15 2,6-dimethylcyclohexanone......................... 16 2-phenylcyclohexanone............................. 16 2,2-dimethylcyclohexanone......................... 16 Quantum YieldyDeterminations Relative Quantum Yields for Ketone Disappearance.............................. 19 Quantum Yield for Product Appearance.............. 20 Absorbances of Ketones and Their Products......... 21 Effects of Photolysis Time on Cyclopentanone and Cyclohexanone................................. 21 Canprehensive Table of Results.................... 22 DiBCUSSimOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO 23 Effects of Alpha Substitution..................... 23 Effects of Ring Strain............................ 23 Comparison of Alkoxy Radical System to System Studied................................. 25 Effects of Beta Substitution...................... 26 mperj-mentaIOOOOOCCOOO0......OOOOOOOOOOOOOOOOOOOOOOOO 31 ApparatUSOOOOOOOOOOOOOOOOOOOOOCOO0..0.00.00.00.00. 31 Chemicals........................................ 32 Procedures....................................... 33 Cyclopentanone at High Conversion................ 37 Singlet Reaction for Cyc10pentanone.............. 38 Cyclopentanone at Low Conversion................. 38 Cyclohexanone at High Conversion..................4O Singlet Reaction for Cyclohexanone............... 4O Cyclohexanone at Low Conversion.................. 41 2-methylcyclohexanone at High Conversion......... 42 2-methylcyclohexanone at Low Conversion.......... 43 3amethylcyclohexanone at High Conversion......... 44 3amethylcyclohexanone at Low Conversion.......... 45 3,5-dimethylcyclohexanone........................ 46 3,3,5-trimethylcyclohexanone..................... 46 2,6-dimethylcyclohexanone........................ 47 2-phenylcyclohexanone............................ 47 2,2-dimethylcyclohexanone........................ 48 Actinometry...................................... 50 Relative Quantum.Yields for Disappearance of Ketone........................................ 52 Quantum.Yields for Ketone Disappearance at Low Conversion................................ 53 Quantum.Yields for Product Formation............. 54 Literature CitedOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO 79 vi List of Figures Pig. Page Stern-Volmer Plot for Quenching of 1 Cyclopentanone at High Conversion................... 55 Stern-Vblmer Plot for Quenching of 2 Cyclopentanone at Low Conversion.................... 55 Stern-Vblmer Plot for Quenching of 3 Cyclohexanone at High and Low Conversions........... 56 SterneVblmer Plot for Quenching of .4 Zamethylcyclohexanone at High and Low Conversions... 57 Stern-velmer Plot for Quenching of 5 3dmethylcyclohexancne at High and Low Conversions... 58 6 Stern4V01mer Plot for Quenching of 3,5-dflmethylcyclohexanone........................... 59 Stern-Vblmer Plot for Quenching of A 7 3,3,5-trimethylcyclohexanone............ . ........... 60 Stern—Vblmer Plot for Quenching of 8 2,6-dimethylcyclohexanone........................... 61 Stern-velmer Plot for Quenching of 9 2-pheny1cy010hexanone00OOOOOOOOOOOOOOOOOO0.0....0... 62 Stern-Vblmer Plot for Quenching of 10 2’2-dj-methy1cyc10hexanone..0OOOOOOOOOOOOOOCOOOOOOOOI 63 11 NMR spectrum of 4-Pentenal.......................... 64 12a IR Spectrum of 4-Pentenal (4000-1750 cm‘l).......... 66 12b IR Spectrum of 4-Pentenal (2000-800 cm'l)........... 67 13b IR Spectrum of 2-Methyl-5-Heptenal(2000-800 cm‘l)...‘ 68 13a IR.Spectrum.of 2-Methyl-5-Heptenal(4000-1750 mm'l).. 69 14 Disappearance of Cyclohexanone versus Appearance of 5-Hexenal as a Function of Time.................. 70 Fig. Page Disappearance of Cyclopentanone versus 15 Appearance of 4-Pentenal as a FUnction Of TmeOCOOOOOOOOOOO00.0.00...OOOOOQOQQQQQ 71 16 VPC Trace for Cyclopentanone Photolyzate.. 72 17 VPC Trace for Cyclohexanone Photolyzate... 73 18 VPC Trace for 2-phenylcyclohexanone mOtOlyzateoeoeoo00000000000000.0000.eeeoo 74 19 VPC Trace for 2-methylcyclchexanone Phot01yzat800000000000OOOOOOOOOOOOOO0.0... 75 20 VPC Trace for 3amethylcyclohexanone motOJ-yzateOOOOOOOOOOOOOOOOOOOOOOOOOOOO... 76 21 VPC Trace for 3,5-dflmethylcyclohexanone mOtOI-yzateooooeooeeeeooeooooeoeoooeoooooe 77 22 VPC Trace for 2,2-dimethylcyclohexanone motOIyzateOOOOOOOOOOOOOOOOOOOOOO0.0.0.... 78 Table II III IV VI VII VIII XI XII XIII XIV XVI XVII XVIII XIX List of Tables Effect of Quenching on Cyclopentanone.......... Effect of Quenching on Cyclohexanone........... Effect of Quenching on 2-methylcyclohexanone... Effect of Quenching on 3-methylcyclohexanone... Effect of Quenching on 3,5-dimethy1cyclo- hexarloneOOOOOCOOCOOOOOOOOOOOOOOOOOOOOOOO...0..O Effect of Quenching on 3,3,5-trimethylcyclo- mxanoneOOCOOOOOOOOO0.0.0.0...OOOOOOOOOOOOOOOO. Effect of Quenching on 2,6-dimethylcyclo- hexanoneIOOOOCOOOOOOOOOOOOCOOOOOOOOOOOOOOOOOQDO Effect of Quenching on 2-phenylcyclohexanone... Page 14 14 14 15 15 15 16 16 Effect of Quenching on 2,2-dimethylcyclohexanone16 Relative Quantum Yields for Disappearance of Ketone at High Conversion................... Quantum Yields for Disappearance of Ketone at Low Conversion....................... Quantum Yields for Product Formation........... Absorbances of Ketones and Their Products at 31303....0...OOOOOOOOOOOIOOOOOO...0.00.00... Effect of Photolysis Time on Cyc10pentanone and CyCIOhexanoneOOOOOOOOOOOOCOOOOOOOOOOO...0.. Comprehensive Data of Quantum Yields and Reaction Rates from.Low Conversion Data........ Quenching of 0.2M Cyc10pentanone at High Conversion..................................... Singlet Reaction of Cyclopentanone............. Photolysis of 0.15M Cyclopentanone at Low Conversion (Run 1)......................... Photolysis of 0.2M CyclOpentanone at Low Conversion (Run 2)......................... it .19 20 2O 21 38 38 39 Table XXII XXIII XXIV XXVI XXVII XXVIII X”CI XXXII XXXIII XXXIV XXXV Photolysis of 0.2M Cyclohexanone at High conversionOOCCOOOOOOOOCOOOOOOOOOOOOOOOOO Singlet Reaction of Cyclohexanone............ Photolysis of 0.1MTCyclohexanone at Low Conversion (Run 1)....................... Photolysis of 0.2M Cyclohexanone at Low Conversion (Run 2)....................... Photolysis of 0.2M'24methylcyclohexanone at High conversj'on...‘OOOOCCOOOOOOOOOOOOOOOOO Photolysis of 0.1MI2amethylcyclohexanone at Low Conversion (Run 1).................... Photolysis of 0.2M 2-methylcyclohexanone at LW conversion (Eu-In 2)....0000000000000000 Photolysis of 0.2Mfi3amethylcyclohexanone at High ConvergionOOCOCOOOOOOOOOOCOOOOOOOOOOO Photolysis of 0.15M 34methylcyclohexanone at High conversion.OOOCOOOOOOOOOOO0.0...O...O Photolysis of 0.1MISamethylcyclohexanone at Low Conversion............................ Photolysis of 0.1M 3,5-dimethylcyclohexanom at Low Conversion............................ Photolysis of 0.1Mi3,3,5-trimethylcyclo- hexanone at Low Conversion................... Photolysis of O.UM 2,6-dimethylcyclo- hexanone at Low Conversion................... Photolysis of 0.1MI2-pheny1cyclohexanone at Low Conversion............................ Photolysis of 0.1M 2,2-dimethylcyclo- hexanoneooooooooooooooooo00000000000000...000 Actinometer Analysis for Quantum.Yield of Ketone Disappearance at Low Conversion.... ’2; Page 40 40 41 41 42 43 43 44 45 45 46 46 .48 51 Table Page XXXVI Relative Quantum.Yields for Disappear- ance of Ketone at High Conversions........ 52 XXXVII Quantum.Yields for Disappearance of Ketone at Low Conversion.................. 53 XXXVIII Quantum.Yields for Product Formation...... 54 Introduction Cyclic five- and sixamembered ring ketones under- go photoisomerizations which involve cleavage of the bond between the carbonyl and the alpha carbon‘ (1). The same type of phenomenon can be observed in the alkoxy free radical system (2). The weak absorption band at 280-360m1, noted in ketones, arises from the n,“n'2'r transition (3). The breakage of that bond involves a non-bonding electron on oxygen being promoted to an antibonding pi orbital. The alkoxy radical system should serve as a good.model for the n31“!r triplet state, since both species posseseann electron deficient oxygen atom. This statement has been validated by comparing relative reactivities of hydro- carbons toward both the n;fl$ triplet states of ketones and tertiary butoxy radicals. Relative reactivities of hydrocarbons depend on the 0-H bond strength in the same fashion toward both abstracting species (4). The photolysis of cyclopentanone in the vapor phase has been the subject of several investigations over the past 25 years (5-8). It was shown by Benson and Kistiakowsky (9) that the products of its photolysis are carbon.monoxide, ethylene and cyclobutane. Later work (7) then showed 4-pentenal to be an important product also. From the consideration of the mass balance relationships, three photochemical processes were proposed. ‘—"'"' D'CO + 202H4 + hv -— >- C0 + cyclobutane It was concluded the products were formed from the excited singlet state (10). Cyclohexanone was then studied in the vapor phase also (11). Photolysis of cyclohexanone yielded products such as carbon.monoxide, ethylene, propylene, cyclo- pentane, pentene and 5-hexena1. o —">’ CH2=CH(CH2)ZCH3 + C0 __ p. cyc10pentane 4- CO + hv .__. p. 02H4 + 03H5 + CO With both ketones, the hydrocarbons and the un- saturated aldehydes were not totally quenched by the addition of oxygen (12). It: was concluded the primary photochemical processes of cyclopentanone and cyclohex- anone are very similar in the gaseous state, in that the reaction is occuring primarily from the excited singlet state 0 3 Until recently, the photochemistry of the cyclic ketones in the condensed phase has not been throughly examined. There are several factors which would cause a difference between vapor and liquid phase photolysis. In the liquid state, there is much more association between nearest neighbor molecules; therefore, there would be many'more collisions between.molecules than in the gas- eous state where the molecules are more dispersed. With more of these collisions occuring, whether it be between two ketone molecules or between a ketone and a solvent molecule, there would be a rapid loss of vibrational energy in the electronically excited ketone molecule. Another factor to be considered is the possibility of chemical reaction between the excited ketone molecule and a solvent molecule. Finally, it has been observed (13,14) in the condensed phase that cyclopentanone shows evidence for the existence of triplet state molecules, which were not observed by Srinivasan in the gaseous phase (15). The facts mentioned here show the need for careful quantitative experimentation to be nude on the liquid phase reactions of cyclic ketones. Pitts and co-workers (16) have recently performed such determinations on cyclopentanone and cyclohexanone. They reported triplet lifetimes of .04 x 10'7sec and .83 x 10‘7sec for cyclopentanone and cyclohexanone,respectively. The photolysis of cyclohexanone has been well studied in the liquid phase by several workers, and formation of 5-hexenal, presumably by an intramolecular rearrangement, was found to be the major product (17). The formation of 5-hexenal is capable of being quenched, while formation of 2-methylcyclopentanone, another prod- uct, is not. This suggests that these two products occur from two different excited states of cyclohexanone; 5-hexenal from the triplet state and the unquenchable Zamethylcyclopentanone from the singlet state (17). Cyclohexanone behaves sflmilarly in 1-octene solution to yield quenchable 5-hexena1, and unquenchable 2amethyl- cyclopentanone (18). When cyclohexanone is photolyzed in aqueous solution, a reaction has been observed(19,20) which leads to the formation of caproic acid, the total reaction being the addition of one molecule of water and the cleavage of the ring ketone. C) 4’ H20 all: ‘> ~CH?) (CH2 )4COOH During recent investigationsiby Yates (21) on cyclic ketones of the form, CH20H2(CH2)nCszO, it was found that a ketene is produced as a major isomeric product: C7 ll 4640 re. J“ 0.,“ CH3 . L -— >- (cu; (cup—J (c Quinkert (22) has related the difficulty of ketene form- ation in the case of cyclopentanones relative to cycldhexanones. Cyclopentanone (17), dihydrocarvone (23), men- thone (24), and 24methylcyclohexanone (25) also undergo a reaction to yield an unsaturated aldehyde. In an aqueous alcoholic solution, 2amethylcyclohexanone and menthone undergo a light induced hydrolysis to form the cpen chafln acid as shown here (24):c (9 OK i1» LIL AC“3(C“1):C°°H It is generally assumed that in the condensed phase, the photolytic dissociation of acyclic ketones is retarded by collision deactivation(26) and that the radicals formed are removed, at least in part, because of the cage effect postulated by Franck and Rabinowitch (27). If the rate of recombination of the radicals produced is not faster than the rate with which the alkyl radical center loses its original disymmetry, racemization should then occur in a ketone which.has an assymetric alpha carbon. In the early forties, Butenandt and co-workers (28) found that l7-Ketosteroids suffer a partial photo- epflmerization at C1313 CHJO . " l3 ~Ala> . ' e H . u Since then, many cases of this type of behavior have been observed (29,30,31). Other investigations have shown that camphor photolyzed in aqueous alcdholic solution (32) leads to alpha-csmpholenic aldehyde as the major product. /\cuo I x0 4- aqueous alcoholic 3:. >- ‘ solution $2?- This photoreaction of camphor is analogous to alkenal formation from monocyclic five- and six-membered ketones. Many authors have pr0posed theories to account for these photochemical transformations (33,34,35,36). Srinivasan originally reported that 2-methylcyclohexanone gave only m—s-heptenal (36), in conjunction with his postulated concerted mechanism, to yet be described. Alumbaugh and co-workers (37) have since reported that 2,6-dimethylcyclohexanone yields both gig- and ging- 2-methyl-5—heptenal in the same ratio independent of the starting materials geometry. Recently, Pritchard and co-workers (38) have re-examined 2-methylcyclohexanone and proved the prod- ucts of photolysis to be both the gig: and Eggggg alde- hydes. In keeping with. the‘relative thermodynamic stabilities of secondary versus primary radicals (39), the preference of the 1 ,2 bond cleaving rather than the 1,6 bond, is more than 50 times greater for the former. Frey (40) has investigated the photochemical decomposition of trans- 2,3-dimethylcyclopentanone and noted products of cis and trans 1,2-dimethylcyclobutane. Since both were formed, it seems that a biradical inter- mediate is necessary to account for them. 0 21>. [I [i The two mechanisms which have been postulated to account for the behavior of acyclic ketones are described here. One involves a concerted type rearrangement (36,41) as shown in Equation Scheme 1, and the other postulates a biradical intermediate (42) as indicated in Equation Scheme 2. Both postulated.mechanisms account for the observed aldehydic product. C9 Equation Scheme 1 C /‘&'{"'”C H1. (oz). ““91; 't / ”(‘3 Q 0 / ”Q \é Equation Scheme 2 (up), cut—9 :0“, a“ / ' Hz. (a) QH/c \Cfl ‘ There are at least four points to give support to the biradical mechanism. It is known that ketones do‘ undergo the alpha type cleavage, both aliphatic and alicyclic (43,44,45,46,47). The racemization of the 17- ketosteroids could only occur if the alpha bond became ruptured to allow rotation about the 013 bond and thus lose its assymetry. If a concerted type mechanism were Operative, the 013 centre would remain intact. The bi- radical mechanism also allows 2,6-dimethylcyclohexanone to yield equal amounts of cis and trans alkenal, indepen- dent of the geometry of the starting ketone; 'Ihe quench- ability of the observed products by oxygen or dienes points to an intermediate involving unpaired spins, which strong- ly suggests a 2-step mechanism. The method employed in this investigation is the quenching of the triplet product by a diene; a method used and explained by many workers (48,49). Dunion and Trumbore (50) have shown that most of the observed isomerization of the cyclic Icetones can be quenched by suitable triplet quenchers. This fact allows us to quan- titatively study the photoisomerization of the cyclic ketones. The schematic representation of the process is shown here : it K° + hv ____> K1 * . K1 loco! K3* 'k 165* + Diene .34.» K0 + Diene:5 K3* .5» Products K3* .51...) KO By the application of steady state approximation, the Stern-Volmer equation correlates these values into a usable form: ¢o/¢a = 1 + kq‘Z’EQ] ./lr_=//ér+,kd where 110 is the quantum yield for the formation of alde- hyde in the absence of quencher and 16a is the quantum " yield for formation in the presence of a quencher, i.e. a diene. A linear plot occurs when the ratio 1230/ 08 vs. [Quenchea is made; this presupposes the aldehyde is formed only from the triplet state. The slepe of this plot is then equal to kq’I’. The bimolecul ar quenching constant in the solvent benzene has been calculated to be 5.0 x 109 liter/mole sec (51). The lifetime of the triplet state can then be found. Piperylene was used as a quencher, in most cases, since it is a very efficient acceptor of the triplet energy of ketone triplets, but does not quench their singlet states (52). This particular investigation was involved mainly with 05 and C6 cyclic ketones, but a discussion about them would not be complete without mentioning results of experimentation on their 04, C7, and 08 analogs. Cyclobutanone has been studied by several workers (53,54) and quantum yields for products obtained were calculated. The yield of C3H6 was found to increase with decreasing cyclobutanone pressure and with shorter wavelengths, while the yield of 56;;- C3H6 was unaffected. A mechanism 10 involving formation of C3H5 from an excited triplet cyclobutanone, possibly involving a diradical intermed- iate, has been proposed. K + hv —4>1K 1K -—> c-C3H6 + C0 1K ——> 02114 + 011200 1K.i:$r3x 3K —-)°CHZCH20H2. + co oCHZCH20H2--—4>'CH30HCH2 3K + 'M-——9»K + ‘M Bernard (55) and Srinivasan (25) made an investigation on cyclooctanone, and noted that photolysis in cyclohexane solution yielded reduction products of cyclooctanol and an unidentified bicyclooctanol. In the pure liquid phase, a mixture of products were observed: hv ‘ M. er I. Srinivasan (56,25) also studied the photolysis of the cycloheptanone system and found it to decompose yielding a similar array of products. CH2=CH(CH2)4CH0 hv 0 -—->- or art 0 Q 11 Turro and Southam (57) also studied cyclobu- tanone in methanol and found that ring expanded cyclic acetals were formed. This work shows an intermediate bi- radical leading to carbene formation. H C=g=0< 11?. "'7‘0 112. p. D 8.25. D- go“ CHECHz The investigation presented here was begun to examine various cycloalkanones, and to determine how ring size and substitution on them.effects the photo- chemistry of the triplet states. The effects of this substitution on the quantum yields was also studied. The systems that were chosen to accomplish this effort are cyclopentanone and various methyl and phenyl sub- stituted cyclohexanones. The available information on the photochemistry of substituted cyclopentanones and cyclohexanones indicates that the presence of one or more alkyl substituents on the ring does not lead to any new photochemical reactions; but as this paper shows it does effect rate of reaction and quantum yields for various products. It is hoped that through this study, the photoreactivity of cyclic ketones may be better understood. Results It has been discussed in the introduction how the Stern-VOlmer equation is applied and what results can be derived from it. The importance of quenching studies on these ketones is essential, since very little is known about the relationship between triplet state reaction rates and molecular structure. The quantum.yield for these triplet state reactions are also important. I. Quenching Studies A degassed solution of each ketone in benzene was irradiated at 3130 R. Vapor phase chromatograph traces of the irradiated samples are displayed in Fig- ures 13A22.-In.most cases, the major product peak appears at approximately one-half the retention time of the parent cyclic ketone. In the presence of quencher, the area of the major product peak is reduced. That this peak corresponds to the aldehyde was established by adding some authentic aldehyde to the irradiated sample and observing an increase in area of the major product peak. The major products of some of the ketones 4-pentena1, 5-hexenal, and 2-methyl-54heptenal were -13- prepared by irradiation of cyclopentanone, cycldhexanone, and 2,6-dimethylcyclohexanone in benzene, respectively. These products were isolated by preparative vapor phase chromatography. Comparison of their infra-red spectra to those presented by Srinivasan, and appearance of aldehydic and vinyl protons in their NMR spectra, were deemed suf- ficient for their identification. It was assumed that the analogous Vpc product peak for the other ketones cor- responded to the expected 1D-alkenals. In all cases, the pungent odor associated with an aldehyde was easily de- tected. Other unidentified peaks were observed to be formed in low yields for all ketones studied. . Quenching studies were performed by irradiation of 0.1-0.2 M cyclic ketones at 3130/4, in degassed benzene solution containing a known concentration of an internal standard and various known concentrations of quencher, either piperylene or 2,5-dimethyl-2,4-hexadiene. Relative quantum yields of alalkenal were found at low conversion and of ke- tone disappearance at high conversions. The slopes of the Stern-Volmer plots, together with triplet lifetimes calcu- lated from them, are contained in Tables I-XII. Details for each study are in the experimental section of this thesis. For each ketone, almost all zD-alkenal formed could be quenched by high concentrations of piperylene or 2,5-dimethyl-2,4- hexadiene; however, not all ketone disappearance could be quenched due to small amount of singlet reaction occuring. A. Cyclopentanone Table I. Effect of Quenching on CycloPentanone Estona Time Irradiated % Reacted Slope(111"l)a T(sec) 72(sec “T .2 m 68 hrs. 54 73 21 4.2x10‘9 2.4::108 .1 M 6 hrs. 11 % 46 9.3x10‘9 1.1::108 .1 m 5% hrs. 10.2 % 48.4 9.7x10'9 1.1::108 3value equal to k‘T'and calculated from.s10pe of Stern-Volmer plot. B. Cyclohexanone Table II. Effect of Quenching on.Cyclohexanone Ketone Time Irradiated % Reacted Slapewfjfla T(sec) #(sec‘l) .2 m 90 hrs. 43 9% 292 8.3::10"8 1.2::107 .1 M 10 hrs. 14 9% 147 2.9210"8 3.4x107 .1 M 9% hrs. 12 76 155 3.1::10'8 3:21:17 .1 m 9 hrs. 10.2 m 151 3.0:t10”8 3.3::107 3value given is equal to k‘7’and was found using Stern- VOlmer plot. C. ZéMethylcyclohexanone Table III. Effect of Quenching on Zemethylcyclohexanone Ketone Time Irradiated % Reacted Slepe(MIl)a‘7’(sec) ' sec'l) .2 M 75 hrs. 77 % 6.3 1.2::10"9 8.0::108 .1 M 6 hrs. 14 7. 10.9 2.2::10’9 4.61108 .1 M 9 hrs. 18 96 10.3 2.1x10"9 4.8::10 aValue equal to khjfl -15- D. 3-Methylcyclohexanone Table IV. Effeottof Quenching on 3-Methylcyclohexanone Ketone Time Irradiated 9% Reacted 810pe(M"l)El T (sec) 3;}(sec'1 .2 m 114 hrs. 42 96 137 2.8:;10"8 3.6x107 .2 m 93 hrs. 26 7% 240 4.8x10"8 2.1::107 .l M 12 hrs. 11 96 209 4.0110- 2.5117 a‘Value given equal to 1: q? and found using Stern- Volmsr plot . E . 3 , 5-Dimethylcyclohexanone Table V. Effect of Quenching on 3, S-Dimethylcyclohexanone Ketone. Time Irradiated 76 Reacted Slepe(M'1)aFT( sec) :‘g sec"l .1 M 22 hrs. 10% 206 4.1::10'8 2 . 4x107 aValue equal to k (11' and calculated from slaps of Stern- Volmer plot . F . 3 , 3 , 5-Trimethylcyclohexanone Table VI . Effect of Quenching on 3,3, 5-Trimethylcyclohexanone Ketone Time Irradiated % Reactedl Slope (waft? ( sec) .1 M 40 hrs. 10% 199 4 . 9x10”8 a'Value equal to k ‘17 and calculated from slaps of Stern- Volmer plot. G. 2,6—Dimethylcyclohexanone Table VII. Effect of Quenching on 2 ,6—Dimethylcyclohexanone LKetoneITime Irradiated. 9'0 ReactedISlopem- l)EIT(sec) I-if(sec"1—)—I I .1 MI 4 hrs. 9 76 I 5.37 I1.1x10‘9I 9.3x108I aValue equal to kq1‘and calculated from Stern- Volmer plot. H. 2-Phenylcyclohexanone This particular ketone did not give the aldehyde as the major product, because the major peak observed could not be reduced when concentrations of 1M.piperylene were used. The peak representing the aldehyde was located in a manner already described. Table VIII. 3 f Effect of Quenching on 2-Phenylcyclohexanone IKetoneITime IrradiatedI 9% ReactedI Slope(M"1)1T (sec) Ii: (sec 1)J I .1 MI 3 hrs. I 10 % I 15.2 I3. 0x10 9It}. 3xlO—I aValue equal to k‘1'and found using the Stern- VOlmer plot. I. 2,2-Dimethylcyclohexanone Table IX. Effect of Quenching on 2,2-Dimethylcyclohexanone IKetoneI Time IrradiatedI 96 ReactedI Slope(m’1)1’z’(soc) gees-1)] .1 HI 2 hrs. I 8. 2 at] 2. 79 I5.6x10‘.’m 1. 8x109I alue equal to k‘t'and found using Stern-Velmer plot. -17.. Special consideration was given to 3-methylcyclo- hexanone. When this molecule absorbs light, it seems two triplet products should occur: 0 O 9 I: "I; [:::L\ __———%>,/[:;:J' #. [:T’JLI‘ A B Twenty-five grams of this ketone were diluted in benzene and then Dhotolyzed. The major product was isolated and its NMR did not show the presence of allylic methyl. Srinivasan (58) originally reported the absence of the "B" isomer, which is in agreement with the results of this author. II. Quantum Yield Determinations Quantum yield studies were perfOrmed by irradiation of 0.1-0.2 M ketone at 3130140 in degassed benzene solution containing a known concentration of an internal standard. An actinometer solution was used to determine the intensity of the light. The actinometer tubes consisted of 0.1-0.2 M cis-piperylene and a known mount of acetone in a degassed hexane solution. The quantun yield of sensitized cis- to trans-piperylene isomerization was taken to equal 0.56 (59). The irradiated ketones were analyzed by 17130 for pro- duct concentration and ketone concentration. The actinometer solutions were malyzed for conversions of cis to trans- piperylene. Fran this information, can be calculated the absolute ‘18- quantum.yields for product appearance and ketone dis- appearance can be calculated. Those values which were found for ketone disappearance are tabulated in Tables X and XI. The quantum yield for disappearance of the cyclic ketone would be insignificant toward describing reaction pathways by which the parent ketone can be converted to aldehydic product. To give meaning to the values, the quantum yield for product appearance are given in Table XII. It was noted, as the length of irradiation time increased, the value for quantum yields of product ap- pearance decreased. To determine the cause of this observation, two sets of experiments were performed. One consisted of isolating various aldehydic products and obtaining their absorbsnce at a given concentration. The absorbences for parent ketones were also obtained, and then compared. A second eXperiment consisted of irradiating samples of both cyclopentanone and cyclo- hexanone with an internal standard in a degassed benzene solution, and analyzed for ketone and product concen- 132¢ions at given time intervals. The graphic represen- tation of data in Table XIV can‘be cited in Figures 14 & 15 . A comprehensive table of data obtained in this investigation is given in Table IV. 19 mm. .m "U a. 00. m. OuAHM mo. 0.: ROM 0.. _N 90 No. v0 90 mm. mm "0 oo._ 3 "0 mm. mm 80 d m>C3um zo_mmm>zoo&m mzoamx ll zo_.mmm>zou 19.1 e.< mzoumx do muz£3mm X mmm<._. 20 Table XI Quantum Yields for Disappearance of Ketone at Low Conversion Ketone %Conversion Relative ¢-k Absolute ¢ k 2,6-dimethylcyclo- 21 % 1.00 .56 hexanone cyclopentanone 24 % .50 .28 cyclohexanone 13.6 % .23 .13 zamethylcyclohexanoné 18 % .89 .50 3-methylcyclohexanona 15 % .14 .08 3,5-dimethylcyclo- 12 % .059 .033 hexanone 3,3,5-trimethylcyc101 8.3 % .043 .024 hexanone 2-phenylcyclohexanone 22.4 % .91 .51 2,2-dimethylcyclo- 22 % .95 .54 hexanone ' Table XII Quantum Yields for Product Formation Ketone ghoto. 7oConver- [Product] Eroa/hr ¢+p 1me sion cyclopentanone 3 hrs. 9.5% .0092M .00307MI .24 cyclohexanone 2 hrs. 5.4% .OOZIM .00105M .09 2-methylcyclohexanone 1 hr. 6.4% .0050MC .00501M .42 3-methylcyclohexanone 4 hrs. 6.2% .0016Mi .00034M. .034 3,5-dflmethylcyclo- 12%hrs. 5.7% .0008M .00007M .005 hexanone 2,6-dimethylcyclo- 1 hr. 6.1% .0048M .0048M .40 hexanone 3,3,5-trimethylcyclo- 12%hrs. 2.7% .0003M .00002M .0017 hexanone ' . 2-pheny1cyclohexanone 1 hr. 13% .OOOSM .00052M’ .04 2,2-dimethylcyclo- 2 hrs. 8.2% .0096M .00478M .42 hexanone -21.. Table XIII. Absorbagces of Ketones afid Their roducts at 3130 Substrate Concentration Wavelength Absorbance E; .1031 M 3130 X 1.40 13.6 .1113 M 3130 R .92 8.3 .1180 M 3130 R 1.10 9.3 .0575 M 3130 R .468 8.2 .1187 M 3130 R 1.10 9.3 .1031 M, 3130 2 .87 8.4 .1090 M 3130 3 .95 8.7 .1358 M 3130 2 1.98 14.6 .2010 M 3130 2 2.896 15.5 .2000 M 3130 x 2.713 13.6 Table XIV. Effect of Photolysis Time on Cyclopentanone and Cyclohexanone Ketone Photolysis Time Ketone Product 0 hrs. 0.1158M 0.0000M Q 3.0 hrs. - 0.105414 0.009210 [:3 8.5 hrs. 0.0843M. 0.0224M 14.0 hrs. 0.0680M 0.0322M 26.0 hrs. 0.0497M. 0.0445M 0 hrs. 0.1110M 0.0000M 9 3.0 hrs. 0.100511 0.003211 [:J 8.5 hrs. 0.0930M 0.0044M 14.0 hrs. 0.0880M 0.0043M 26.0 hrs. 0.0780M 0.0036M 22 Table XV CMprehensive Data of Quantum Yields and Reaction Rates from Low Conversion Data Ketone 04‘ 0.1) 1/‘2’ (for -k) l/‘Z’ (for +p) ' >=o .27 .24 2.4 x loasec'"1 1.1 x 1083ec'”1 a =0 .13 .09 1.2 x 107sec”1 3.3 x 107sec'1 b =0 .50 .42 3.0 x 10888C-1 4.7 x 10859.61 ° ,0 .03 .03 ....... 2.5 x 107sec'”1 7 -1 :0 .03 .005 ------- 2.4 x 10 sec Q“) .56 .40 ------- 9.3 x lossec"1 7 -1 9:0 .02 .002 ------- 2.5 x 10 sec 0 8 -1 O; .51 .04 ------- 3.3 x 10 see fig .54 .42 - ------ 1.8 x logsec‘”1 a Average of two values b Average of three values ° Average of two values Discussion It seems evident from.observing all of the data presented, that there are several phenomenon that need to be explained: 1) the effect of substitution on the alpha carbon, 2) the effect of beta carbon substitution, 3) effect of ring strain, 4) competitive absorption of the unsaturated aldehydes with their parent ketone. When a ketone molecule absorbs a duantum.of energy, a n electron is promoted to a pi* state. The excited sing- let rapidly crosses over to the triplet state ketone molecule. various reactions can then occur from.this excited state. The equilibriums involved depend on the size of the ring and the degree of substitution at the alpha carbon. When.molecu1ar models of cyc10pentanone and cyclo- hexanone are compared, the ring strain in cyclopentanone is obvious. The rate data shows the effect of this ring strain, with cyclOpentanone 3 times more reactive than cyclohexanone. The enhanced reactivity can be attributed to the relief if ring strain when the molecule goes 23 24 to the acyclic biradical. The recoupling reaction can have a pronounced effect on the quantum yield of a reaction. Depending on how“much recoupling competes with furthur resetions,the observed quantum.yield will naturally be smaller than the true quantum.yie1d with which the excited state reacts. The degree of substitution at the alpha carbon is important in determining the triplet state reactivity. It is known that a tertiary free radical is more stable than a secondary or primary. This stabilization of free radicals can be considered the driving force of the re- action. Observation showed the formation of triplet product from cyclohexanone was less than that obtained from cyclopentanone, indicating that recoupling and ketene formation occur better in the 1,6 biradical. The observed quantum yield for deethylcyclohexanone is larg- er than cyclopentanone or cyclohexanone, and 2,2-dimethyl- cyclohexanone is larger than all of the ketones studied. Substitution on the alpha carbon also plays an flmportant role in determining how long lived the excited state will be. The fact that the rate of reaction of the trip- let 2,6—dflmethylcyclohexanone is twice as fast as the rate for Zamethylcyclohexanone, can be attributed to the degree of alpha substitution. This correlation can be followed through all alpha substituted ketones studied; 25 i.e. 2-methylcyclohexanone is 15x faster than cyclo- hexanone, and 2,2-dflmethylcyclohexanone is twice as fast as 2,6-dimethy1cyclohexanone. The effects of alpha substitution on reaction rate are summarized in the following table. Ketone Relative Rates Cyclohexanone 1.0 Zamethylcyclohexanone 14.3 2,6-dimethylcyclohexanone 28.0 2,2-dimethylcyclohexanone 54.2 2-phenylcyclohexanone 10.0 Many workers (60,61,62,63) have studied rates of H abstraction in cyclic ketones. In using alicyclic t-hypochlorites, the rate of this hydrogen abstraction by alkoxy radicals occurs in the order primary< second- ary<3tertiary. In the following sequence of reactions, it was found that the CS reacts faster than the C6° OCI . 0 \O \. 26 Alkyl groups are lost from tertiary alkoxy radicals in the sequence Me<‘g o . ‘ 0 o o This observation would account for the quantum yield of product formation being about oneshalf that of cyclohex- anone. | In 3,5-dimethylcyclohexanone and 3,3,5-trimethyl- 'cyclohexanone the number of abstractable hydrogens is .reduced even more and hence a notable decrease in quantum yield for the formation of their respective triplet products. During this investigation, it was observed 28 repeatedly that quantum yield values were subject to change depending on length of irradiation time. It has been suggested that as the concentration of the aldehydic product builds up in the solution, the reac- tion to produce more product is suppressed, presumably by the unsaturated aldehyde itself, as well as by the ketene by-product. From.the analysis of the data shown in Table x111&x1¥,and that in Figures 14&15 , it is postulated that the aldehyde acts more as an "internal filter" rather than as a quencher. The aldehydic prod- ucts, in most cases, absorbs light as strongly as their parent ketone as shown by absorbsnce data, given in the results section. In a recent paper by Yates (64), it was conclud- ed that a major product of cyclohexanone photolysis is the ketene. 0 CD 47‘) I |.‘ Cr ~> This reaction was discussed briefly in the introduction, but a conclusion can be made from.this observation. When ketones are.chosen carefully, the formation of aldehydic products can be hindered; e.g. 3,3,5,5-tetramethylcyclo- hexanone or dihydrofuranone. In these two cases, products are formed which clearly arise from the ketene. This ketene formation explains the observed low quantum yields for triplet product formation in cyclohexanone. However, 29 ketene formation can also be used to explain other quantum yield values observed for other ketones studied. 'When substitution occurs at the alpha position, the rate to form aldehyde becomes more competitive with ketene formation. Substitution at the beta position also probably affects competition between ketene and aldehyde formation. As substitution at the beta position becomes larger, the excited state yields mainly ketene. More work is needed in this area to determine quantitatively the magnitudes of these effects. Pitts recently (65) made a quantitative examination on cyclopentanone and cycl ohexanone. The values he ob- tained for lifetimes can be compared to those obtained in this study. The cyclopentanone values were directly com- parable , but the value for cyclohexanone was not. Little experimental techniques were explained, so an absolute discrepancy is hard to determine. It is very likely, however, that the length of irradiation of the ketone solution explains the difference in data. The dependance of photolysis time on cyclohexanone has already been discussed. Much investigation is still required for these types of systems to be completely understood. Substitution on the cyclopentanone ring would lead to very interesting results, with the expectation that the variations in re- activity and quantum yields could probably be explained 30 in an analogous manner as the cyclohexanone system has been. One very interesting point arises from the fact that 2-phenylcyclohexanone cleavage may be affected by substitutions on the phenyl ring. The various enhance- ments and deactivations would prove to be a very worth- while study. The larger ring systems such as in the case of cyclooctanone and cycloheptanone also show . promise for future study. During this investigation, the larger ring systems were briefly examined. Photolysis of cycloheptanone for 114 hours yielded only an 8% disappearance of ketone, and photolysis of cyclooctanone for 144 hours gave only a 2%1disappearance of ketone. These systems should be studied more completely, but it seems that as the ring size increases from a six- membered through an eightamembered ring, tendency for the cleavage of the alpha bond diminishes and trans- annular reactionstake precedence. Experimental I . Apparatus All of the infra-red spectra were obtained on a Perkin-Elmer'Model 2373 recording spectrOphotometer using sodium chloride cells. Nuclear magnetic resonance' spectra were determined either in carbon tetrachloride or neat using a JEOLCO C-6OH high resolution recording instrument with tetramethylsilane as an internal stand- ard. The ultraviolet data were collected on a Spectronic "20" recording apparatus. Vapor phase chromatOgraphy analyses were made using four different instruments: the F&M Model 700 with a thermal conductivity detector using a i" x 5' QFl column, a Varian Series 1200 and an Aerograph Hy-Fi 600-D both equipped with flame ionization detectors us- ing QFl and Carbowax columns. A F&M Model 810 equipped with an Infotronics CRS-llHB electronic integrator was the fourth system.used for analyses. Two different experimental setdups were used to carry out photolysis experiments. Photolytic experiments on a preparative scale were conducted in a water-cooled quartz immersion well using a 450 watt Hanovia medium pressure mercury arc lamp. All quantitative irradiation experiments were performed on a.merry-go-round apparatus(6£b 31 32 equipped with a 450 watt Hanovia medium pressure mer- cury arc lamp contained in an aqueous solution of .OOZM potassium.chromnte with one percent potassium.carbon~ ate to filter out all but the 3130 3 mercury line. The entire unit was placed in a water bath contained at 25°C. A schematic representation of the unit is shown below: All Filter 31303 I l ‘ 5 Solution only ——-+ Sample Cell Source II . Chemicals Piperylene and iBOprene were obtained from Aldrich and then purified by distillation. The 2,5- dimethyl-2,4~hexadiene, also obtained from.Aldrich, was purified by repeated recrystallization from.itself. All three quenchers were examined by vapor phase chromato- graphy to insure maximum purity. The solvent benzene and the internal standards were repeatedly treated with concentrated sulfuric acid, then with 10% aqueous sodium hydroxide solution, follow- ed by several washings with distilled water and finally distilled over phosphorous pentoxide. All of the ketones, except cyc10pentanone, were obtained from.Aldrioh Chemical Co. Cyclopentanone was 33 purchased from K & K.Chemical Co. The ketones were purified by distillation through a 12" Vigereux column, except 2-phenylcyclohexanone which was purified by recrystallization from hexane. The ketones were checked for purity using Vpc techniques. III. Procedures The product of photolysis of cyc10pentanone, 4- pentenal was prepared in a similar manner to that of Srinivasan (10), except in the liquid phase rather than the gaseous phase. The material was collected on the F 8: M Model 776 Prepmaster Jr. using a 20% Carbowax columm.at 85°C. The infra-red spectra taken (See Figs. 12a & 12b) agrees with that described by Srinivasan. As a furthur diagnostic tool, an NMR.was taken (See Figure 11) and also supported the structure of 4-pentenal. The 5-hexenal, which is the product formed in the photolysis of cyclohexanone, was prepared in a sim- ilar manner described by Srinivasan (10). The aldehyde was again collected on the F 81 M Model 776 Prepmaster Jr. using a 20% Carbowax column at 100°C. The infra-red spectrum was taken and compared to that taken for 4- pentenal; they were superimposable. The NMR spectrum was also taken and was found to support the 34 structure of 5-hexenal. TWenty-five grams (.198 moles) of 2,6-dimethylcyclo- hexanone were diluted to 100 ml with benzene and placed in an immersion well. The solution was irradiated for 48 hours using a pyrex filter. The excess benzene was taken off by distillation, and the product collected on the F&M Model 776 already described, at 110°C. The infra-red spectrum.(Figs. 13a & 13b) and NMR were taken. Analysis of these spectra supported the structure of 2-methyl-5-heptenal. TWenty-five grams of Samethylcyclohexanone were di- luted to 100 ml with benzene and then photolyzed in an.immer- sion well apparatus for 90 hours. The excess benzene was distilled off to concentrate the ketone and its products. The aldehydic products was seperated on the PM! Model 776 Prepmaster at 100°C using a 20% Carbowax column. An NMR spectra was taken to aid in identification of the product collected. As concluded by other workers (25,67), there was no indication of the other isomer, Samethyl-S-hexenal. Ten grams of 2-phenylcyclohexanone was dissolved in benzene and photolyzed for 6 hours. The benzene was taken off using a rotary aspirator. Attempts to isolate and identify this product of photolysis using the EEMiModel 776 Prep- master were unsucessful. 35 The method of H.O. House and V. Kramer (68) was used to prepare 2,2-dimethylcyclohexanone. The product was isolated using a F&M Model 776 preparative chromato- graph at 85°C with a 2 :75 Carbowax column. B. Quenching Studies For the 2,2-dimethylcyclohexanone, one stock solution 0.67M.in ketone and 0.035M in pentadecane, as standard, was prepared by weighing the appropriate amount of ketone and standard in a 25ml volumetric flask and diluting to volume with benzene. Stock solution. 0.10M in piperylene was prepared similarly. A 2ml portion of the ketone stock solution was pipetted into each of sev- en lOml volumetric flasks, one of which was immediately filled to volume with solvent. Quantities of l to 3, S and 8 ml of each of the quencher solutions were pipetted into each of the other flasks before they were diluted to volume. Then 3.0ml of each diluted solution was placed in separate pyrex tubes with a syringe. The tubes were standard 13x100mm culture tubes which had been washed and dried before being constricted about one inch from the top to allow sealing. The tubes with the samples in them were attached to a vacuum.line and put through three freeze-pump-thaw cycles before being sealed in vacuo at .005mm. Samples were prepared quite similarly for the 36 other ketones except using different standards, for usable Vpc analysis, and different concentrations of quencher for measurable Stern-Vblmer plots. In any given run, degassed tubes containing various concentrations of quencher were irradiated in parallel with two samples containing only ketone and standard in benzene solution, all for the same amount of time. Irradiations were performed in the merry-ge- round apparatus, already mentioned, consisting of a rotating turntable with the light source and filters at the center and windows of identical area allowing radiation to enter the various samples ports. The entire apparatus was immersed in a water bath, and the temp- erature during irradiation was held at 25°C. The percentages of singlet reaction were deter- mined for cyc10pentanone, cyclohexanone, and 2-methyl- cyclohexanone. Stock solutions of these ketones and their respective standards were prepared similarly to the method already described. Tubes containing no quencher and others containing high concentrations of quencher were prepared and irradiated in an identical manner. From. analysis of these solutions, the per cent singlet re- action can be calculated. The experimental results are shown here in Tables XVI- XXXIV. Table XVI Quenching of 0.2M Cyclopentanone at High Conversion Standard=0.05M tridecane Irradiation Time: 68 hours Per Cent conversion: 54% VPC Conditions: Injector=200°C O Detector3250 C Oven=llO 0 Column: FFAP He flow rate: 50 ml/min Apparatus: F&M Model 700 TM] K/Sa %Reacted * 73Triplet Reacted jag/[6 b 0M(un- photoly- 1.868 O zed) 0 m .860 54.0 46.7 1.000 5x10'3m. .951 49.1 42.5 1.115 1x10’2M 1.003 46.4 40.3 1.192 2x10‘2m 1.116 40.3 34.7 1.407 3x10'3m 1.171 37.3 32.2 1.541 4x10'2M 1.250 33.1 28.6 1.788 5x10’2m 1.279 31.5 27.3 1.900 aChromatOgraphic area molar ratio of Ketone/Standard. bThese values represented here have had the singlet reaction subtracted out. See Figure l for Stern-Volmer plot of results. Singlet Reaction of Cyclopentanone Concentration of ketone=0.2M Standard=0.05M dodecane 38 Table XVII VPC Conditions: Same as Table XVI LIsOprena * Irradiation Time 76 Ketone Reacted F K/Sa CM 0 hours 0 1.872 cm 54 hours 53. .876 CM 42 hours 42. 1.071 2“ 96 hours 12. 1.650‘3 2M 6'This is the chromatographic area ratio:of ketone to standard peaks. b Photolysis 0f 0.15M Cyclopentanone at Low Conversion (Run 1) Average of two runs TableXWTII Standard=0.004M.tridecane Irradiation Time: 5% Conversion: 8% VPC Conditions: Injector=180°c Detector3195 Oven: 35 hours 0 0-758 0 at 2°c/m1n Column: 4%QF1;1% Carbowax He flow rate: 25 ml/min Apparatus: Varian "1200" AerOgraph @iperyleng 4 P/S Area Ratio ' +[P] a flo/fla CM .897 .0142 1.00 5.01:10‘3m .665 .0104 1.35 1.02:10'2M, .586 .0093 1.53 2.04:10'3M .491 .0079 1.84 3.06:10'2m. .358 .0057 2.51 aAssuming area to molar ratio of ketone is the same for its aldehydic product. Later experiments showed this to be true. 39 Table XIX Photolysis of 0.2M Cyclopentanone at Low Conversion (Run 2) Standard: .OOSM Tridecane Irradiation Time: 6 hrs. Conversion: 9% o VPC Conditions: Injector: 190°C Detectorg 208 C o Oven: 30 -75 C at 2 C/min He flow rate: 25 ml/min Apparatus: Varian Series "1200" using a 4% QFl & 1% Carbowax column Piperylene] P/S Area Ratio +[Pja fio/fla 0 M .533 .0169 1.00 5.m0"3 I .415 .0132 1.28 1.1::10"2 M .351 { .0111 1.52 2.2::10"2 M .271 .0086 1.96 3.3::10”2 M .216 .0067 2.46 8Assuming the area to molar ratio of ketone is the same for its aldehydic product. Later experiments showed this to be true. 40 Table 10! Photolysis of 0.2 M Cyclohexanone at High Conversion Standard: .05M Tetradecane Irradiation Time: 90 hrs. Conversion: 43% VPC Conditions: Injector: 18530 Detector? 250°C 0 Oven: 40 C-850 C at 2 C/min Column: FFAP He flow rate: 50 ml/min Apparatus: F&M Model "700" .f.____# [M] K/s8L + M Reacted 7 a: Triplet Formed flo/flab 0M(Unpho- tolyzed) 2.016 0% 0% 1.142 43.4 76 38.7 9% 1.000 1. 08x10_3M 1.333 33.9 9% 29.8 9% 1.324 2. 16110 1.419 29.7 9% 26.1 9: 1.552 3. 24x10" 1.440 28.6 94 25.2 % 1.620 4.32:10 3M 1.469 27.2 76 23.8 % 1.725 aChromatographic area ratio of ketone to standard b out. These values have had the singlet reaction subtracted See Figure 3 for Stern-Volmer plot of results for cycle- hexanone photolysis. Table XXI Singlet Reaction of Cyclohexanone Concentration of Ketone: 0.2M Standard: .05M Tridecane VPC Conditions: Same as in Tablelol oven is at 110C except [:Piperyleng * Irradiation Time 73 Ketone Reacted K/Si! 0 M 0 hrs. 0 1.958 0 M’ 24 hrs. 18.2 % 1.602 g g 3; Es. 27.2 9% 1.425 . s. .2 M 97 hrs. 7'1 9% 1'82° 8'These values represent area ratios for ketone to standard Average of two runs b 41 Table XXII Photolysis of 0.1 M Cyclohexanone at Low Conversion (Run 1) Standard: .005 M Tridecane Irradiation Time: 9 hrs. Conversion: 11 % o VPC Conditions: Injector: 185°C Detectorg 200 C Oven: 70 C Column: 4% QFl & 1% Carbowax He flow rate: 25 ml/min Apparatus: Varian "1200" [Piperylene] P/S Area Ratio * +[fl a 130/5258 ‘ 0 M .489 .0106 1.00 1 x 10'3M .422 .0092 1.16 2 x 10'3M .376 .0081 1.30 3 x 10'3M .331 .0072 1.478 aAssuming area to molar ratio for ketone is the same for its aldehydic product. Table XXIII Photolysis of 0.2M Cyclohexanone at Low Conversion(Run 2) Standard: .005M Tridecane Irradiation Time: 6 hrs. Conversion: 7 % 0 VPC Conditions: Injector: 190°C Detectors 200°C 0 Oven2 40 C-85 C at 2 C/min Column= 4% QFl & 1% Carbowax He flow rate: 25 ml/min Apparatus: Varian "1200" ‘ lEPiperylene] ' P/S Area Ratio 4 +[P] a 00/03 0 M .371 .0097 1.000 1.1 x 10'3M .318 .0083 1.166 2.2 x 10‘3M .278 .0072 1.336 4.4 : 10‘3M .224 .0059 1.657 gAssuming the area to molar ratio for the ketone is the same for its aldehydic product. VPC Conditions: Injector: 190 42 Table XXIV Photolysis of 0.2 M 24Methylcyclohexanone at High Conversion Standard: .OSM Tetradecane ’ Irradiation Time= 75 hrs. Conversion: 77 % °c Detector: 250°c Oven: 105°C Column: FFAP He flow rate: 50 ml/min Apparatus: F & M Model "700" a L b fitsoprene] K/S ax Reacted % £331? ¢o/¢a OM(Un.hoto- lyzed 2.089 0 % 0 % ...._ O‘M .472 77 % _ 67.7 % 1.000 5.02x10’3M .504 75.8 % 66.7 t 1.021 1.03x10'3M .561 73 % 64.3 a 1.069 2.06x10'2M .630 69.8 % 61.5 % 1.128 3.09:10'2M .722 65.5 % 57.6 % 1.217 2 M 1.859 11.1 % 0 % “Chromatographic area ratio of ketone to standard bThe singlet reaction has been subtracted out of these values 43 Table XXV Photolysis of 0.1 M. 2—Methylcyclohexanone at Low Conversion(Run 1) Standard: .005M Tetradecane Irradiation Time: 6 hrs. Conversion: 9 % VPC Conditions: Injector: I802C Detector: 200 C Oven: 80 C , Column= 4% @115: 1% Carbowax He flow rate: 25 ml/min Apparatus: Varian "1200" [Piperylene] ‘ P/S Area Ratio +[P] 8‘ > 00/03 0 M 1.273 .0117 1.000 1.1x10'3M 1.127 .0104 1.130 2.2x10'2M 1.015 .0093 1.250 3.3x10‘3M .940 .0086 1.350 1.5 M 0.0 «mm -——-— aAssuming area to molar ratio for ketone is the same for its aldehydic product Table XXVI Photolysis of 0.2M 2-Methylcyclohexan0ne at Low Conversion(Run 2) Standard: .005M Tetradecane Irradiation Time: 9 hrs. Conversion: 12 % VPC Conditions: Same as inoTable XXV,except Oven is 85 C IEPiperylene] P/S Area Ratio + [£3 a fio/fla O'M 1.451 .0187 1.000 1.1 x 10'3M 1.331 .0171 1.090 2.2 x 10‘3M 1.138 .0147 1.280 4.4 x 10‘3M 1.051 .0135 1.446 aAssuming area to molar ratio for the ketone is the same for its aldehydic product See Figure 4 for SternPVolmer plot of these results. Photolysis of 0.2 M 34Methhlcyclohexanone 44 Table XXVII at High Conversion Standard: .OSM Tetradecane Irradiation Time: 93 hrs. Conversion: 25 % o VPC Conversion: Injector: 195°C Detector: 250 C Oven: 115°C Column: FFAP He flow rate: 50 ml/min Apparatus: F &.M:Mode1 "700" Egh/fidj K/s° %:K Reacted % Triplet eb/Cgb Formed $$£3§ hOtO- 2.125 0% 0 5 0 M: 1.586 25.4 % 23.3 a 1.000 1.1r10’3M 1.691 20.4 5 18.7 % 1.270 2.2110'3M 1.755 17.4 a 15.9 % 1.522 3.3x10’3M 1.766 16.8 a 15.4 % 1.792 4.4x10'3M 1.902 15.2 a 13.9 % 2.030 aChromatographic area ratios of ketone to standard b values The singlet reaction has been subtracted out of these Phot 45 Table XXVIII olysis of 0.15M 3:Methylcyclohexan0ne at High Conversion Standard: .05 Tetradecane Irradiation Time: 114 hrs. Conversion: 42% o VPC Conditions: Injector: 200 C Ap' Detector:0250°C Oven: 110 C Column: FFAP He flow rate: 50 ml/min [Piperylene] K/Sa ’ %1K Reacted ’ % Triplet aratus: F d M Model “700" L ‘¢ .¢ b Formed o/ §fi_ 0M(un hoto- 1yzed 2.051 0 % 0 % ‘01n 1.04x10'3fl 2 . 08x10'3M 3.12:10’3M 1.185 1.273 1.358 1.429 42 % 37.9 % 33.8 % 30.3 % 38.6% 34.8% 31.0% 27.8% 1.000 1.125 1.278 1.443 aChromatogr bThe single ted. Phot aphic area ratio of ketone to standard. t reaction, equal to 8.3%, has been.subtrac- Table XXIX olysis of 0.1 M 3+Methyloyclohexanone at Low Conversion Standard: .OOSM Tetradecane Irradiation Time: 12 hrs. Conversion: ll % .VPC Conditions: Injector: 185°C Detector:0200°C Oven: 110 0 Column: 4%.QF1 & 1% Carbowax He flow rate: 25 ml/min LEiperylen§g_ Apparatus: Varian "1200” f + [P] 20mm 0 M 2.12x10'3M 3 . 18x10‘3M 4 . 24:10'311 .5 M P/S Area Ratio .0109 1.00 .149 .106 .0077 1.41 .091 .0066 1.64 .0056 1.96 .076 .001 .0009 pm See Figure 34methylcyc 5 for Stern-Volmsr plot of these results on lohexanone. 46 Table 100: Photolysis of 0.1 M 3,5-Dimethy1cyclohexan0ne at Low Conversion Standard: .005 M Pentadecane Irradiation Time: 22 hrs. (full arc) Conversion: 10 % o VPC Conditions: Injector: 195 0 Apparatus: Varian "1200" Detector: 209°C Oven: 30-100 0 at 2°C/min Column: 4% QFl & 1% Carbowax He flow rate: 25 ml/min [Piperylene] P/S Area Ratio +[p] '5 . pic/ea 0 M. .0806 .0083 51:000‘ 1.01x10‘3M, .0666 .0068 1.210 2.02x10‘3M .0566 .0058 1.421 3.03x10‘3M .0500 .0052 1.610 .5 M .003 .0003 26.8 aAssuming area to molar ratio for ketone to be the same for its aldehydic product. See Figure 6 for Stern-Volmer plot of these results. Table XXXI Photolysis of 0.1 M 3,3,5-Trimethy1cyclohexanone at Low Conversion Standard: .005M Pentadecane Irradiation Time: 40 hrs.(fu11 arc) Conversion: 5 % 0 VPC Conditions: Injector: 185°C Detector: 209 C o Oven: 60-100 0 at 2 C/min Column: 4%>QF1 & 1% Carbowax He flow rate: 25 ml/min Ap aratus: Varian."l200" [Piperylene] P/S Area Ratio 4 + [E] a CO/CL 0 M’ .0680 .0027 1.000 1 x 10'“3 M .0569 .0023 1.194 2 x 10’3 m: .0484 .0019 1.404 3 x 10‘3 M .0424 .0017 1.605 .4 M .0000 --- aAssuming area to molar ratio for ketone to be the same for its aldehydic product. 47 See Figure 7 for Stern-Volmer plot of results in Table XXXI. Table XXXII Photolysis of 0.1 M.2,6-Dimethylcyclohexanone at Low Conversion Standard: .005M Tridecane Irradiation Time: 4 hrs. 'Conversion: 13 % °C VPC Conditions: Injector: 190°C Detectorg 200 0 Oven: 65 0 Column: 4% QFl & 1% Carbowax He flow rate: 25 ml/min Apparatus: Varian "1200" Eperylene] ’ P/S Area Ratio + [P] a 00/953 0 M 1.712 .0141 1.000 1 x 10"2 m; 1.628 .0134 1.052 2 x 10’2 M. 1.545 .0127 1.109 3 x icgz M; 1.471 .0121 1.164 aAssuming area to molar ratio for ketone to be the same for its aldehydic product See Figure 8 for Stern:701mer plot of results in Table Standard: Conversion: 7 % Table mm Photolysis of 0.1 M 2-Pheny1cyclohexanone at Low Conversion .005M Heptadecane Irradiation Time: 3 hrs. VPC Conditions: Same as in previous gable except Ingector: 2000 even: 155 0 _5 a LPiperylene] P/S Area Ratio P/S - j +[P] Cgéfli O‘M .0775 .0755 .00101 1.000 1.1r10’3M .0665 .0645 .00085 1.170 2.2x10’3M .0598 .0578 .00078 1.321 3.3x10’3M .0510 .0490 .00066 1.521 2 m .002 n-.- m... -.-- aChromatographic area ratio minus the singlet reaction. Assuming area to molar ratio for ketone to be the same for its aldehydic product. 48 See Figure 9 for Stern-Volmer plot of results in Table XXXIII. Table’IXXXIV Photolysis of 0.1 M 2,2-Dimethylcyc10hexanone at Low Conversion Standard: .005M Pentadecane Irradiation Time: 2 hrs. Conversion: 8.1 % 0 VPC Conditions: Injector: 19000 Detector: 208 C o Oven: 65-100 0 at 2 C/min Column: 4% QFl 8c 1% Carbowax He flow rate: 100 ml/min Apparatus: F 8: M Model "810" [Piperylene] P/S Area Ratio » P/S-Ssa 4 +[Ifl b 4 950/163 0 M: 1.646 1.631 .0137 1.000 1 x 10'2.M. 1.604 1.589 .0133 1.027 2.1 10'2‘M. 1.557 1.542 .0129 1.057 3 x 10"2 M 1.517 1.502 .0126 1.084 5 x 10‘2 M. 1.446 1.431 .0120 1.141 8 x 10‘2 M: 1.346 1.331 .0112 1.224 aChromatographic: area ratio minus the singlet reaction bAssuming area to molar ratio for the product is the same as the parent ketone See Figure 10 for Stern-Volmer plot of these results. A 0.2 M solution of cycloheptanone containing .0511 tridecane was photolyzed for 117 hours in the presence of various concentrations of quencher. After that time, the tubes were analyzed as follows. K/S for Unphotolyzed solution: 2.047 K/s for Photolyzed solution: 1.850 A detailed set of data was not collected for this ketone. 49 A 0.2 M solution of cyclooctanone containing .05 thexadecane in benzene was prepared and photo- lyzed in a similar manner to all ketones studied. The system.was photolyzed for 144 hours with only 2.3% reaction occuring. A detailed set of data was not col- lected for this ketone. 0. Quantum Yields Ten.milliliter.volumetrics were weighed and then charged with different ketones and their respective st- andards, weighed to the nearest ten-thousandth gram. The volumetrics were then diluted to volume with purified benzene. A.3 m1 portion of each was pipetted into sep- erate pyrex tubes with a syringe. The tubes were the standard 13x100 mm culture tubes which had been washed and dried before being constricted about one inch from tap to allow sealing. The tubes were degassed by freeze- pump-thaw cycles before being sealed in vacuo at .005 mm. In order to measure the quantum yields accurate- 1y,eaprecise actinometry method had to be used. Hammond and co:w0rkers (56) made an extensive study on inter- system.cr0ssing efficiencies of various substrates. They deve10ped an accurate method for measuring the quantum yields of triplets in solution. In their experiments,the triplets could be determined by following the isomeriz- ation of some olefin from.its trans- to cis- form or vice versa, as shown below: p<0 KI 50 +4.1) ——>- K‘ .——_I>‘ P(3 K3 + \._._—__/ —:>- K°+ \2/3 I \\==/A3' .—_‘D>- //==J/ -+- \\==// In our experiments, the sensitizor was acetone because it is known to give 100% triplets in solution (70). The amount of these triplets formed was followed by the photoisomerization of cis-piperylene to its trans isomer. The equation used for this calculation is shown below: fl =‘- [A] LNCoc/d ——fl/) where, ff? o< fé?’ [A] is the conversion of cis to trans without back reaction, is the conversion at the stationary state for the glefin (for cis to trans piperylene ’3 0555 is the conversion of cis to trans measured experimentally, is the original concentration of the cis- piperylene. The per 0633 conversion of cis- to trans- piperylene was followed on a 25% 1,2,3-triscyanoeth0xy- ethane 90665 at 50°C. 51 The actinometer tubes were prepared by weigh- ing acetone and cis-piperylene to the nearest ten:thous— andth grams The volumetrics were diluted to volume with purified n:hexane. A 3ml portion was then placed into pyrex tubes and degassed, as in previous experiments. These tubes were photolyzed in a merry-go-round appara- tus simultaneously with the ketones to be studied. With the actinometer tubes present, it is possible to deter- mine the intensity of the 450 watt Hanovia mercury arc lamp. The results are given in the following tables. Tauraxxxv Actinometer Analysis for Quantum.Yie1d of Ketone Disappearance at Low Conversion cis-Pi er 1en Time % Converted In .55 'I E P y a Irradiated 335570;— onv. °/hr .133 1hr 35min 9.47 9% a .1188 .0158 .133 1hr 35min 9.52 % 8‘Average of two runs 52 Table DOCVI Relative Quantum Yields for Disappearance of Ketone at High Conversions Ketone Initial % React- % Lighta Timeb -K/hr. 164‘: Concentration jpn Absorbed Q0 .1058M 61 % 89.5% 12311” .0051 1.00 4:30 .1118M 62 % 97.0% 253m; .0027 .435 One .1112M 28 % 88.2% 25%hrsl .0012 .218 do .1070M 64 % 89.7% 15 hrs: .0046 .88 Q .1000M 21 % 84.6% 253m .00083 .153 Do .1068M 11 % 87.5% 25%hrs .00049 .094 DC .1020M 7.3% 87.1% 25inch .00029 .052 Q0 .1050M 51 % 97.1% 123m .0043 .685 ¢ a’Per cent 1) of light absorbed by respective concentrations. 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I STERN-VOLMER PLOT EOR QUENCH- ING 0F CYCLOPENTANONE AT HIGH CONVERSION o RUN I ARUN 2 3d 0a ID. 0A 2' 0 6» ob/ lo I j 3 4r 2 [0] x IO2 F162 STERN- VOLMER PLOT FOR OUENCH— ING 0F CYCLOPENTANONE AT LOW CONVERSION 56 OHIGH CONV. EXP. ALOW CONV. RUN l X LOW CONV. RUN 2 I l l I 0 I 2 3 4 5 [Q] x IO: {.133 STERN-VOLMER PLOTS FOR GUENCHING 0F CYCLOHEXANONE AT HIGH AND LOW CONVERSIONS 57 0 HIGH CON v. [3 LOW CON v. (I) A LOW cow (2) LST ‘ E! I . L4 4 A '03 " IS] 439 ¢A '02-“ a A O 1.! ‘ El '00 i I | I "1 O I 2 3 4 5 [Q] I: 102 F164 STERN-VOLMER PLOTS FOR QUENCHING 0F Z-METHYLCYCLOHEXANONE AT HIGH AND LOW CONVERSIONS 58 0 HIGH CON V. A LOW CONV. X HIGH CON V. $0 ° ¢A ' . l 9 ' T I I ' I O I 2 3 4 5 [0] x I03 F] GS STE RN-VOLMER PLOTS FOR QUENCHING OF 3-METHYLCYCLOHEXANONE AT HIGH AND LOW CONVERSIONS 59 I . . 0 I 2 3 [0] x IO e F166 STERN-VOLMER PLOT FOR oUENCH- INC OF 3,5-DIMETHYLCYCLOHEXANONE 3 7 60 ele- > O I.0 . , , j 0 I 2 3 4 [0] x I03 FIG? STERN~VOLMER PLOT FOR QUENCH- ING OF 3,3,5- T R I METHYLCYC LOHEXANONE 61 Ll“ as "00 I' 2 3 4 [o] x IO2 F‘GoBSTERN-VOLMER PLOTS FOR QUENCH- ING OF 2’6-DIMETHYLCYCLOHEXANONE u' l‘ Il‘llllll I .II III. ill I 62 LB: |.6- l.4* I.2- "% I {'2 2 3 4‘ [32] x IO *7ng STERN-VOLMER PLOT FOR QUENCHIZ- ING OF 2- PHENYLCYCLOHEXANONE MO 63 mzozu§raw§oIN.N ,uo eziuzuoo men 8.... $597255 0. .07.. NO. x how m e n N A _ o . . . I t 0.. so r I .. mm.— é) lllll I‘I|I if I. I I | tlnll {I 0"! l ‘0 It}... A‘C’Illru. ICOOI 0". It! I d T 0 d . . v. I .- oIl’ I: Co Pa ab 3.1.: Fe So I Po. - . .eb- :1 I _ — I 4 J I I a I I I 4 s I I 7 _ I I I q . . — I . . — _ F _ _ _|‘ 4 s q 4 . 4 d 1 a e u I s . 1 1 q .4. J8 58 § ”00 .8 .-_.. .4. «o r are 8 In I: via-C! a. 03-209 kl or: 5 a.. has. «as» a. mi. Anew nip-AW nrNIIInIF o 8:33 .r.... . .. I akin-25m he“ .. - -. I A .n 1:: 52933: -3. I a: .5556 0.. I I 30 assets... :93. .. - - 8.. 330.33: M, mun. . . a: 2.2.0.32 7.”. I I” .3 .53.»: >5 “I - . . n53» _ \N S!“ yep-:8 23...... 0.)! Sn '1‘“!- .-q f. C ’ .2. .2. s 2--..-_ _-_- -. .2 -. - - so 3311:. ch we no so 6W 0 b I I 1 Po .4. To: 222 mtmnsmcz o... atmzdmzrr .Tzoomt Iooos 223.23-: no zomaomdm mH IHm2IN no somaomdm as 3:07”. arzoorozmoonan oo o 8.0. oo.N . 00-: 00.2 ope. ooom -. 3 x, : EDNVGHOSSV 69 9-56 omtéoos szEuI-m-;IE2-N no 23535 5 uzm:oumu oo.m_ ooom 03.3 00.3 comm 009. 5 3 ts EDNVQH 058 V NEE. mo ZO_._.UZD..._ 4 m4 4 mzozU no muz UZOZU “.0 wuz<¢._O._.OIQ mzozu mom mu ®_ .07; 2:2 _._ o. m m p o m w m m _ b L b F 72 C .232: 73 UP._O._.OIn_ MZOZU mo...— mu w Cd; 74 m._.._ O._.OIn_ mzozU._ >ZMIQ IN .222 m m m w ‘— :0 mob. “mu/um... Un; $.07”. 75 m._.._O._.OIn_ mZOZu4>IhmEIN mom mu3>IEz m m mZNZBo o m _ v n . L . m . 2N. __ 0. ml. 0 a .2— p p 1b O on S /. mzNzoFoza mzoz3>152_o-m.n mo... 33.: ua> .Ndl .z . 2 m. N. __ o. w + w m .v n m _ p r phi b b p p w . 1. 77 78 MENBEOIQ mzoqumzodbixfiz.o-~.m mom mus”: um>NNOC 2.2 o P w VN I U w m II‘ N \/ m o: -1 N 0 LI... 10. 11. 12. 13. 14. 15. 16. 17. 18. Literature Cited S.W. Benson and G.B. Kistialcowsky, J.Am.Chem.Soc., 93, 80(1942). C. Walling and A. Padwa, J.Am.Chem.Soc.,_8_3_, 2207(1961). M. Kasha, Discussions of the Faraday Society, 2, 14(1950). Wm. A Pryor, Free Radicals, McGraw-Hill Inc., New York, (1966! p. 1653'. 0.D. Saltmarsh and R.G.W. Norrish, J.Chem.Soc., 455(1935). F.E. Blacet and A. Miller, J.Am.Chem.Soc.,Z_?_, 4327(1957). R. Srinivasan, J.Am.Chem.Soc., _8_1._, 1546(1959). M.C. Flowers and H.M. Frey, J.Chem.Soc., 3953(1959). S.W. Benson and G.B. Kistiakowsky, J.Am.Chem.§oc., g2, 80(1942). R_. Srinivasan, J.Am.Chem.Soc., g1, 4344(1961). R. Srinivasan, J.Am.Chem.Soc., fl, 2601(1959). J.R. Dunn and K.0. Kutschke, Can. J. Chem., 23, 725(1954). S.R. LaPaglia and 8.0. Roquitte, Can. J. Chem. ,_l_t_l_, 287(1963). S.R. LaPaglia and 8.0. 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Phys, Chem., 9.2.9 No. 3, 945(1966). il\“HimUljlfllflujll[IJHJIHlliHllllHHltllHHIuh 177 5731