PART 1 Pfim‘QN-“C S?£:<.siz~m CGUFLQEVECE PART 1'? QARJEQNESM {me REARifiéfiéGEi’a-‘fims we m gstQFYL AME? NEQPENWL gvsmms Timers {'01‘ “to Degree of 55. D. REICEHGRN STH‘E UHWERXKTY Chester E. Orzech, Jr. 1968 THESIS LIBRAR y MlChlgan Sta cc nfinnsky This is to certify that the thesis entitled PART I PROTON-13C SPIN-SPIN COUPLING PART II CARBONIUM ION REARRANGEMENTS IN THE ngROPYL AND NEOPENTYL SYSTEMS presented by Chester E. Orzech, Jr. has been accepted towards fulfillment of the requirements for Ph.D. degree in Chemistry 6f (“Waxy Major professor Date December 15, 1967 0-169 4......- ..-.. . - _....———M.- .A._.. -.... I'll-Illa; , L ‘rtll' Illu‘llltxlll‘l, ABSTRACT PART I PROTON-13c SPIN-SPIN COUPLING PART II CARBONIUM ION REARRANGEMENTS IN THE ngROPYL AND NEOPENTYL SYSTEMS by Chester E. Orzech, Jr. PART I Several investigations have been directed toward elucidation of the factors affecting proton-13C couplings over one, two, and three bonds both in saturated and un- saturated systems. The short-range coupling, J13CH' has been studied extensively on account of the relative ease of detection by high resolution n.m.r. of the natural occurring 1% l3C. The general linearity between JISCH and fractional s-character of the 13C hybrid atomic orbital has led to the conclusion that the Fermi contact term is essentially the sole contributor to the coupling (1). Long-range proton-13C coupling has been studied less extensively. In this case laC enriched (>10%) compounds must be used. Several workers (2,5) in the field concluded that JISCCH follows s-character when the l"3CCH angle is tetrahedral only. No correlation has been found for J13CCCH° Chester E. Orzech, Jr. A synthesis of many lsC enriched compounds was under- taken in order to measure their proton-13C couplings and attempt a correlation. The compounds were either prepared from lithium or magnesium alkyls and 13C02 Obtained from enriched barium carbonate or purchased directly. The com- pounds were purified either by vapor phase chromatography or recrystallization. One-, two-, and three—bond couplings were studied. The one- and three-bond couplings were measured together in neopentyl (-lSCH2-) compounds and the two-bond couplings in acetyl (13C=O) compounds. A Varian Associates A-60 n.m.r. spectrometer was used at about 58°C (ambient) to measure the proton—13C couplings from the proton spectra. The one- and two-bond couplings, JlSCH and J13CCH' follow s-character fairly well, with one exception. When the substituent is a group with angular-dependent atomic orbitals (p,d,f), both J13CH and J13CCH do not behave in a linear fashion with s-character. In the case of the three-bond coupling, J13CCCH' no linear relation is obtained at all. Dihedral angle effects have been shown to be of little significance, whereas it appears J13CCH is extremely sensitive to the HCC and CC13C angles. Also a bent-bond approach seems to correlate very well qualitatively with the data. Chester E. Orzech, Jr. PART II In reactions which are known to generate carbonium ions the neopentyl system always gives products resulting from the t-amyl cation. EfAmyl products and isg-pentenes, but no 1,1—dimethylcyclopropane, are found. The 1-propyl system on generation of a carbonium ion leads to l— and 2-propyl products, propene, and cyclopropane. It has been suggested that many carbonium ion rearrange- ments proceed yia_methyl-bridged nonclassical ions (I) or protonated cyclopropanes (II), since cyclopropanes are found \/ c 953 I x + /* ; ______ :\ T I II to be products of many of these reactions. Evidence for methyl—bridged nonclassical carbonium ions and protonated cyclOprOpanes has been scarce. By appropriately labeling 1-propyl and neopentyl compounds, generating the carbonium ions, and analyzing the products for label position and percent, protonated cyclopropanes, symmetrical (II) or bridged (III), could be detected, if formed. / A +\ \ \ >C\C—/;:C< :_: —c\ /:£\—:-H: etc. /’ \\ III Chester E. Orzech, Jr. For studying the 1-propyl system, 1-propylammonium—1,1- g2 and 1-propylammonium-2,23g2 perchlorates were prepared and deaminated with nitrous acid. For the neopentyl system, neopentylammonium-i,1-§2 and neopentylammonium-1-13C perchlorates were prepared and deaminated. Also studied by solvolysis were neopentyl-1,1-d2 and neopentyl-l-lsc tosylates, and neopentyl-l-lsc iodide. Mass Spectral analysis of the l-propanol obtained from the deamination of 1—propylammonium-1,1-g2 perchlorate gave the following isotopic composition for the d-carbon: 96.1% g2, 0.8%‘d1, and 3.1% do. The 1-propanol from 1-propyl- ammonium-2,2jd2 perchlorate gave: 1.2%‘g2, 0.9%‘d1, and 97.9% do. Since protium-deuterium positional rearrangements occurred, and reversible 1,2-shifts are ruled out on the basis of the percentage ratios of the products and the fact that 2-aminopropane did not yield any 1-propanol, a protonated cyclopropane (II) or bridged ion (III) accommodates the re- sults quite well. About 5% of the 1-propanol was found to be rearranged at 400 and 5% at 00. The tramyl alcohol obtained from the deaminations and solvolyses was found by mass spectral analysis to contain all the label at C-5. This eliminates the possibility of protonated cyclopropane intermediates. If a protonated cycloprOpane had formed some of the label would have been Chester E. Orzech, Jr. found at C-4. Also, no 1,3-hydride shifts occurred, because no label was found at C-1. Apparently the only reaction occurring is a 1,2-methyl shift on account of the very favor- able primary to tertiary ion rearrangement. REFERENCES 1. M. Karplus and D. Grant, Proc. Natl. Acad. Sci. U. S., g§J 1269 (1959). 2. G. J. Karabatsos, J. D. Graham, and F. Vane, J. Phys. Chem., §§, 1657 (1961). 3. J. Ranft, Ann. Physik, 9, 124 (1962): $9, 599 (1965). PART I PROTON—13C SPIN-SPIN COUPLING PART II CARBONIUM ION REARRANGEMENTS IN THE ngROPYL AND NEOPENTYL SYSTEMS BY Chester EU]OrzeCh, Jr. A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Chemistry 1968 ~L§ A) U ‘3‘ Q": {N 0 ACKNOWLEDGMENTS The author desires to express his most earnest appreciation to Dr. Gerasimos J. Karabatsos for his guid- ance and interest during the course of this study. Grateful acknowledgment is given to the Petroleum Research Fund of the American Chemical Society whose grant provided financial aid from June 1961 to August 1961 and to the National Science Foundation for the period September 1961 to June 1962 and whose fellowship program provided funds from September 1962 to August 1964. Appreciation is also extended to Seymour Meyerson of the American Oil Company for the numerous mass spectral analyses. *************** ii TABLE OF CONTENTS Page PART I PROTON-13c SPIN-SPIN COUPLING INTRODUCTION . . . . . . . . . . . . . . . . . . . . 1 RESULTS. . . . . . . . . . . . . . . . . . . . . . . 6 DISCUSSION . . . . . . . . . . . . . . . . . . . . . 12 One—bond Coupling . . . . . . . . . . . . . . . 12 Two—bond Coupling . . . . . . . . . . . . . . . 14 Three-bond Coupling . . . . . . . . . . . . . . 16 (A) Dihedral Angle . . . . . . . . . . . . 19 (B) Angle e and e' . . . . . . . . . . . . 21 (C) Bent Bonds . . . . . . . . . . . . . . 22 EXPERIMENTAL . . . . . . . . . . . . . . . . . . . . 26 Acetoxime (13C=N) . . . . . . . . . 26 Acetone-2, 4- -dinitrophenylhydrazone (13C=N). . . 26 2, 4-Dinitrophenylhydrazine Reagent. . . . . . . 26 t-Butyl methyl ketone . . . . . . . . . . . . 27 t-Butyl methyl ketone- 2, 4-dinitrophenylhydra— zone (1C=N) . . . . . . . . . . . . . . . 27 Acetic acid— 1-13C . . . . . . . . . . . . . . . 27 Acetamide (13C=O) . . . . . . . . . . . . . . . 28 Acetyl- -1-l3C bromide. . . . . . . . . . . . . . 28 Acetyl- -1-13C Chloride . . . . . . . . . . . . . 28 Acetyl- -1-13C iodide . . . . . . . . . . . . . . 28 Phenyl acetate (13C=O). . . . . . . . . . . . . 29 prethoxyphenyl acetate (13C=O) . . . . . . . . 29 pritrophenyl acetate (13C= O) . . . . . . . . . 29 N- -Phenylacetamide (13C=O) . . . . . . . . . . . 29 t-Butyl alcohol (13COH) . . . . . . . . . . . . 29 Methyl acetate-1-13C. . . . . . . . . . . 50 Alkyl and aryl acetates (13C=O) . . . . . . . . 50 2 5 S-Trimethyl-2-13C—butene-1. . . . . . . . . 50 2, 5, 5-Trimethyl-—2-butano1-2-13C . . . . . . . . 30 t-Butyl iodide (13C- I). . . . . . . . . . . . . 31 Neopentane(-13CH3). . . . . . . . . . . . . . . 51 iii TABLE OF CONTENTS - Continued 5,5-Dimethylbutanol—1,1fig2—2-13C. . . . 5,5-Dimethylbutyl-—1,1-g2-2-13C acetate. 5, 5-Dimethy1butyl- -1, 1- -%2-2—13C bromide. 5, 5-Dimethylbutyric—2- Neopentyl- -1- Neopentyl- -1-13C Neopentyl-1-13C Neopentyl-1-13C Neopentyl- -1-13C Neopentyl- -1-13C Neopentyl-1-13C Neopentyl- -1-13C 3C acid. . . . acetate . . . . . . . Remethoxybenzoate . . benzoate. . . . . . . Ernitrobenzoate . . . sulfite . . . . . . . Chlorosulfite . . . . trimethylsilyl ether. bromide . . . . Di-t-butylcarbdnol (13CHOH) . . Di-t—butylcarbinyl acetate (13CO ) . Tri- -t-butylcarbinyl acetate (13C03). _-Butylethylene-1-13C- 2, 2 -d . . . Trimethylacetaldehyde (13C=O) . . . . Methyl trimethylacetate-1-l3C . . . Neopentyl trimethylacetate (13C=O). . Phenyl trimethylacetate (13C=O) . . prMethoxyphenyl trimethylacetate (13C=O) prNitrophenyl trimethylacetate1(13C=O). N-Phenyl trimethylacetamide-1—13C . . . Trimethylacetyl Trimethylacetyl Chloride (13C=O). . . bromide (13C= O) . . . Trimethylacetaldehyde- 2, 4-dinitrophenylhydra- zone (13C=N) . . . . . . . . . . CARBONIUM INTRODUCTION . . . . RESULTS. . . . . . . PART II ION REARRANGEMENTS IN THE ngROPYL AND NEOPENTYL SYSTEMS n-PrOpyl System . . . . . . . . . . . The Neopentyl System. . . . . . . . . DISCUSSION . . . . . The ngropyl System . . . . . . . . . The Neopentyl System . . . . . . . . iv Page 52 52 52 52 55 54 54 54 54 55 55 55 56 56 56 56 57 57 58 58 58 58 59 59 41 47 47 50 57 57 6O TABLE OF CONTENTS - Continued Page EXPERIMENTAL Purification of liquid products . . . . . . . . 64 Preparation Of trimethylsilyl ethers. . . . . . 64 1-Propyl-N,N—diacetamide. . . . . . . . . . . . 65 1-Propyl-N,N-diacetamide-l,1-g2 . . . . . . . . 65 1-PrOpanol—1,1fig2 . . . . . . . . . . . . . . . 65 1-Propy1ammonium-2,25g2 perchlorate . . . . . . 66 1-Propylammonium-1,1fig2 perchlorate . . . . . . 66 Methylmalonic acid. . . . . . . . . . . . . . . 66 Methylmalonic acid-afigrcarboxylegg. . . . . . . 67 Propionic acid-a,dfg2 . . . . . . . . . . . . . 67 Propionamide-d,d-g2 . . . . . . . . . . . . . . 67 Propionitrile-a-d-gz. . . . . . . . . . . . . . 68 1—Propanol-2,2-g2 . . . . . . . . . . . . . . . 68 Deamination of 1-propylammonium-1,1-§2 ' perchlorate. . . . . . . . . . . . . . . . 68 Deamination of 1-propylammonium-2,2-g2 perchlorate. . . . . . . . . . . . . . . . 69 Deamination of 2-propylammonium perchlorate . . 69 Neopentyl—1,1-g2-ammonium perchlorate . . . . . 69 Deamination of neopentyl-1,legg-ammonium perchlorate. . . . . . . . . . . . . . . . 7O Neopentyl-1,1eg2 alcohol. . . . . . . . . . . . 7O Neopentyl-1,1fig2 tosylate . . . l a . . . . . . 71 Solvolysis of neopentyl-1,1igg tosylate . . . . 71 EfButyl lithium . . . . . . . . . . . . . . . . 71 Trimethylacetic-l-lac acid. . . . . . . . . . . 72 Neopentyl-1-13C alcohol . . . . . . . . . . . . 75 Neopentyl-1—13C tosylate. . . . . . . °.° . . . 75 Solvolysis of neopentyl—1-13C tosylate. . . . . 75 Trimethylacetamide-l- 3C. . . . . . . . . . . . 75 Trimethylacetonitrile—1—13C . . . . . . . . . . 74 Neopentyl-1-13C—ammonium perchlorate. . . . . . 74 Deamination of neopentyl-1-l3C-ammonium perchlorate. . . . . . . . . . . . . . . . 74 Neopentyl-1-13C iodide. . . . . . . . . . . . . 75 Solvolysis of neopentyl-1-13C iodide. . . . . . 75 Neopentyl-1-13C Chloride. . . . . . . . . . . . 75 REFERENCES . . . . . . . . . . . . . . . . . . . . . 77 LIST OF TABLES TABLE Page PART I I. Proton-13C Couplings of Various Compounds. . . 7 II. Proton—13C Couplings of (CH3)3C13C Compounds . 8 III. J13 ; . of Substituted Benzalde- IV. Proton-13C Couplings of Various Compounds. . . 25 PART II I. Mass Spectral Analysis of the Trimethylsilyl Ethers of 1-Propanol-1,15g2 Prepared by Lithium Aluminum Deuteride Reduction . . . . . 48 II. Partial Mass Spectra of thmyl Alcohols. . . . 55 III. Percentage Distribution of Label in the EfAmyl Compounds Obtained from the Rearrangement of Neopentyl Compounds. . . . . . . . . . . . . . 56 vi LIST OF FIGURES FIGURE 2a. 2b. PART I One-bond prOton-13C coupling versus s-Character (sp3, spa, Sp) of various com- Two-bond proton-13C coupling versus s-Character of various compounds. . . . . . . Proton n.m.r. Spectrum of neopentyl-1-13C tosylate. . . . . . . . . . . . . . . . . . . J13CH of compounds of structure (CH3)3C13CH2X versus electronegativity. . . . . . . . . . . Three-bond proton-13C coupling of neopentyl- 1-13C compounds versus substituent electro- negatiVitYO . O C C . . C . . . . C C C C . . Three-bond proton-13C coupling of trimethyl- acetyl (13C=O) compounds versus substituent electronegativity . . . . . . . . . . . . . . One-bond proton—13C coupling versus three- bond proton-13C coupling of neopentyl-1-13C compounds . . . . . . . . . . . . . . . . . . PART II Proton n.m.r. Spectrum of neopentyl-1,1:g2— ammonium perchlorate in deuterium oxide . . . Proton n.m.r. spectrum in carbon tetra- chloride of tramyl alcohol obtained from the deamination of neopentyl-1,legz-ammonium perchlorate . . . . . . . . . . . . . . . . . Proton n.m.r. spectrum in carbon tetra- chloride of tramyl alcohol obtained from the solvolysis of neopentyl-1-13C tosylate. . . . vii Page 10 15 17 18 20 52 54 54 PART I PROTON-13C SPIN-SPIN COUPLING INTRODUCTION Several investigations have been directed toward eluci- dation of the factors affecting proton-13C coupling over one (1-15), two (16-19), and three (10,16-20) bonds both in saturated and unsaturated systems. The short-range coupling, JlSCH’ has been studied extensively. The general linearity between J13CH and fractional s-Character of the 3‘3C hybrid atomic orbital has led to the conclusion that the Fermi con- tact term is essentially the sole contributor to the coupling, as suggested from valence bond theory (21). Schoolery (2) has plotted values of J13 versus percent s-Character (see CH Figure 1) to obtain a linear relation. Muller and Pritchard (5), and Gutowsky and Juan (8) have derived the following relationship (equation 1) from valence J13CH = 500 fig c.p.s. (1) bond theory, making several approximations, between J‘BCH and fractional s—Character (0.5) Of the carbon hybrid orbital used in the C-H bond. Additivity relations of substituent effects on J13CH in substituted methanes (6) and formyl (7) compounds have been discovered and interpreted as a direct relation between J13CH and s-Character (8). On the assumption therefore that the 500 __ u} 9a 200 _ U CE 0 1 0') r1 ,3 100 r- 1 l l 25 55 50 Percent s-Character Figure 1. One-bond proton-13C coupling versus s—Character (Spa, spa, sp) of various compounds (2). contact term is essentially the sole contributor to the coupl- ing, fractional s-Characters have been calculated, usually in J13 CH values. three Significant figures, from experimental Deviations from the additivity relations have been observed (5.11.12) especially for highly electronegative substituents such as -F and -OCH3. Douglas (12) has suggested an empirical correction but offers no interpretation. Foote (15) and Mislow (14) have obtained linear empirical relations between J13CH and the C-C-C interatomic angle of saturated cyclic hydrocarbons from C3 to C;2. Long—range proton—13C coupling has enjoyed less atten- tion than Jl3 . From an approximate treatment of J13 CCH' J13CCH and fractional s—Character of the 13C hybrid atomic orbital (Figure 2), Karabatsos and CH and the linearity between co-workers (17) Concluded that contact interaction dominates this coupling when the 18C-C-H angle is tetrahedral. The same conclusion was also reached by Ranft (10,19) and Smith (24). No simple correlation has been found between the three- bond coupling, J13 and the s-Character of the 13C atomic CCCH’ orbital (18,20). Elucidation of the factors affecting long-range proton-13C coupling has been hampered by lack of sufficient and pertinent data. The goal of this research project was therefore to synthesize a large number of suitably substituted 13C enriched compounds, to measure the one-, two-, and three-bond proton-13C coupling wherever applicable, and attempt to interpret the data. »~ 14 m d, 12 o {I} U no 8 ,4 *1 6 4 2 Figure L h— )- l l I 25 55 50 Percent s-Character 2. Two-bond proton-13C coupling versus s-character of various compounds (17). RESULTS Table I summarizes the two‘bond coupling constants and Table II the one- and three-bond coupling constants that were obtained with a Varian Associates A-60 n.m.r. spectrometer at about 560C. The values for the long-range constants, determined at 50 c.p.s. sweep width, are averages of at least three measurements with precision of i.0.05 c.p.s. They were Checked against acetaldehyde, JHH = 2.85 c.p.s. (22,25), and should be accurate to.i 0.05 c.p.s. Short-range constants, determined at 250 c.p.s. sweep widths, are also averages of at least three determinations with precision of i 0.2 c.p.s. They should be accurate to 1.0.5 c.p.s. The Choice of com- pounds with structure I for the two—bond couplings and struc- ture II for the one-bond and three-bond couplings was dictated CH3 —13C (CH3)3C -l3C I II by convenience and by the simplicity inherent in first—order spectra. All spectra had simple, first-order appearance (Figure 5). Neopentyl sulfite and neopentyl Chlorosulfite, as a consequence of nonplanar sulfur, showed nonequivalent methylene protons (25). The syn and anti methyls of acetoxime and acetone 2,4—dinitrophenylhydrazone were assigned according to 6 Table I. Proton-13C Couplings of Various Compoundsa Compound J13CCH (c.p.s.) 1. (CH3)213C=O 5.90 2. (C83)213C=NOH c syn 6.27 anti 6.76C 5. (CH3)213C=NNC5H3(N02)2-2,4 b syn 5.90 anti 7.04b 4. CH3[C(CH3)3]13C=O 5.76 5 CH3[c(CH3)3113C=NNHC583(N02)2-2,4 6.40b 6. CH313C028 6.80 7. CHalSCONHg 6.01 8 CH313COC1 7.58 9 CH313COBr 7.60 10. CH313COI 7.50 11. CH313COZC6H4OCH3-p 7.00b 12. CH313C02C6H5 7.04b 15. CH313C02C6H4N02-p 7.16b 14. C8313C02CH3 4.00 15. CH313C02C285 4.00 16. CH313C02CH(CH3)2 4.00 17. CH313C02CH2C(CH3)3 4.00 18. CH313C02CH2C6H5 ' 4.00 19. CH313C02CH[C(CH3)312 4.00 20. CH313CONHC6H5 6.24d 21. CH313C[(CH3)3C]=CH2 6.40 22. (CH3)213C(OH)C(CH3)3 5.94 25. (CH3)313COH 4.25 24. (CH3)313CI 4.45 aUnless otherwise noted, spectra.were taken in carbon tetra- chloride solution. Benzene solution. 25% Benzene-75% carbon tetrachloride solution, v/y. 50% Benzene-50% dimethylsulfoxide solution, v/v. QJOU‘ Table II. Proton-13C Couplings Of (CH3)3C13C Compoundsa’e Compound J13CCCH J13CH (c.p.s.) (c.p.s.) 1. R-l3CH3 4.65 125.5 2. R-13CH2CD20H 4.15 124.0 5. R-13CH2CD20AC 4.21 127.2 4. R—13CH2CD28r 4.56 151.0 5. R-13CH2C02H 4.44 126.4 6. R-13CH20H 4.48335"f 159.9 7. R—13CH2OAc 4.85 146.1 8. R-13CH20C0C6H4OCH3-p 4.74 145.7 9. R-13CH20COC6H5 4.81 146.1 10. R-13CH20COC6H4N02-p 4.91 146.8 11. R-13CH20TS 5.17 147.9 12 (R-13CH20)2SO 5.16 146.5 15. R-13CH2080C1 5.42 150.0 14. R-13CH2051(C83)3 4.79 159.5 15. R-lBCH2N+H3ClO4- 5.019 145.0 16. R-13CH2C1 5.65 147.9 17. R-13CH28r 5.84 149.1 18. R-13CH2I 5.99 148.0 19. R213CHOH 5.80 156.8 20. R213CHOAc 5.99 147.5 21. R-lsc(CH3)20H 5.59 22. R313COH 5.80 25. R313COAc 5.96 24. R-lSCH-CDg 4.25 25. R-13C(CH3)=CHg 4.00 26. R-13CHO 4.60 171.7 27. R-13COCH3 4.20 28. R213CO 5.72 29. R-l3COZH 4.58 50. R-13C02'K+ 4.56g Continued Table II - Continued Compound J13CCCH J13CH (c.p.s.) (c.p.s.) 51. R-13C02CH3 4.11 52. R-13C02CH2C(CH3)3 4.10 55. R-13C02C5H40CH3-p 4.58 54. R-13C02C6HS 4.60 55. R-13C02C6H4N02-p 4.76 56. R-13CONH2 4.07 57. R-13CONHC6H5 4.58 58. R-13COC1 5.99 59. R-lBCOBr 6.45 40. R-13CH=NNHC6H3(N02)2-2,4 4.40 166.2 41. R-13C(CH3)=NNHC683(N02)2—2,4 5.91 42. R-13CN 5.58 aUnless otherwise noted, spectra were taken in carbon tetra- chloride solution. b . Benzene solution. d25% Benzene-75% carbon tetrachloride solution, v/v. e50% Benzene-50% dimethylsulfoxide solution, v/v. R stands for (CH3) 3C— Dimethylsulfoxide solution. gDeuterium oxide solution. 10 COQumO CH Onwammou ARom .mov o.ofi ma.m no.4 nxanVONMOnaone mEB AamnoaonMOu 4:I:||1\\\\\\1// oodlalahucmmomc MO Esnuommm Ne.o _ nxnmovo mOnHOne I nngOVONMOOne .UCHHOHCOMHumu .H.E.c cououm .m wusmflm UHB¢EOM¢ 11 Karabatsos and co-workers (26). The C15 and trans hydrogens of styrene were assigned according to Pople et_ 1. (27). DISCUSSION One-bond Coupling As the electronegativity, Xa, of the group attached to the 13C increases, J13CH increases in a fairly linear fashion (since Xa's from various sources were used by necessity, some deviations are noted (see Figure 4)). Also, for the neopentyl- 1-13C benzoates, as the para substituent Changes from methoxy to hydrogen to nitro, J13CH Changes linearly from 145.7 to 146.1 to 146.8 c.p.s. However, for the neopentyl-1-13C halides J13CH changes from 147.9 (Chloro) to 149.1 (bromo) to 148.0 c.p.s. (iodo) in a non-linear fashion. Methyl halides Show the same trend (1-9): 150 (ChloroL 152 (bromo), 151 c.p.s. (iodo). This non-linear relationship has been previously interpreted (5) in terms of increases in the percent s-Character of the carbon atomic orbital of the C-X bond as the C-X inter- atomic distance increases. When the 13C is Spa hybridized, JlBCH values are unusually high when a halogen or oxygen is bonded to it; e.g., for formyl fluoride (4) and methyl formate (4), J13CH values are 267 and 226 c.p.s., respectively. That the effect may be detectable even when the halogen is not directly bonded to the 13C is Shown by the higher J13CH values of ortho-substituted benzaldehydes when the ortho substitUent is a group with 12 15 “0302‘ _ -OTS 150‘ '1 ‘Cl "OAC 140 150 JISCH (c.p.s.) 120 J 2.0 5.0 4.0 Xa (Electronegativity) (Figure 4. J13 H of compounds of structure (CH3)3C13CH2X vergus electronegativity. 14 angular-dependent atomic orbitals (p,d,f); e.g., see com- pounds 1; 2,5, and 4; 5 and 6; 10 and 11; and 12, 15, and 14 of Table III. On the basis of the non-linear relationship between Xa and J13CH for the halogens, the large couplings in some spa compounds, and effects of ortho substituents on J13CH of various benzaldehydes, it is evident that s-Characters calculated from J13CH can be unreliable and misleading when substituents having angular dependent orbitals are involved. Therefore, contact interaction may not be the only important coupling mechanism (27). Two-bond Coupling As one can see from Table I, follows s-Character, J13CCH i.e., as the electronegativity of the substituents increases J13CCH increases, e.g., 1, 6, 7, 11, 12, and 15. This is what is to be expected from valence-bond theory (10,17,19). However, as in the case of the one-bond coupling, of J13CCH the compounds containing substituents with angular-dependent atomic orbitals does not follow electronegativity, e.g., 8, 9, and 10. Here again, the contact interaction may not be the only coupling mechanism operative and fractional s—Character cannot be obtained with certainty. 15 Table III. J13C—aldehydic proton of Substituted Benzaldehydes Compound J13CH(C°p'S') 1. CBHSCHO 174.4 2. o-CH3C5H4CHO 175.2 5. m-CH3C5H4CHO _ 175.7 4. p-CH3C5H4CHO 175.2 5. o-ClC5H4CHO 182.1a 6. m+ClC6H4CHO 176.2 7. o-CH30C5H4CHO 179.8 8. m-CH30C6H4CHO 175.4 9. p-CH30C6H4CHO 172.7 10. o-BrC5H4CHO 182.4 11. m-BrC5H4CHO 177.6 12. o-FC6H4CHO 182.0 15. m-FC6H4CHO 177.7 14. p-FC5H4CHO 175.7 15. o-C2H50C6H4CHO 180.2 16. p-HOC6H4CHO 177b aAll liquid samples run neat. Solids run in carbon tetra- chloride solution. bValue from Dr. G. J. Karabatsos. :h I...-..r.lllJ u w . 16 Three-bond Coupling From Table II the failure of a single factor (substituent electronegativity, angle deformation, hybridization) to accom- modate the data is obvious. The most striking observations are: unusually high values for the halogen compounds; in- crease of these values in the order chloro < bromo < iodo, whereas the reverse order is expected (see para-substituted neopentyl benzoates and phenyl pivalates); and some higher values for sp3 and Sp2 compounds than for the sp compound (compare 17, 18, 58, 59, and 42). This and the extensive variation of J13CCCH (from 5.59 to 5.99 c.p.s. when the 13C is sp3 hybridized, 5.72 to 6.45 c.p.s. when spa hybridized, and the value of 5.58 c.p.s. when sp hybridized) Clearly indi- cates that in addition to the s-Character of the 13C hybrid atomic orbital, other factors must significantly affect this coupling. Also, if J13CH is plotted versus J13CCCH for the sp3 neopentyl compounds (Figure 6), no linear relation is ob— tained. Since J13CH follows electronegativity (Figure 1), except for the halogens, one can readily see that s-Character is not the only important factor affecting J13CCCH' Increas- ing electronegativity should increase J13CCCH by virtue of increasing the s-Character (28) of the 13C atomic orbital used in 13C-C bond. The values obtained from the para-substituted neopentyl benzoates (entries 8, 9, and 10 in Table II) and phenyl pivalates (entries 55, 54, and 55), where the effects of factors other than electronegativity are kept constant, 17 18 6'00"' <:> 17 16 (C83)3C13C82x (:) 11 12 5.00% J13CCCH (C'P'S°) p P (I 4.00 I I l 2.00 2.50 5.00 5.50 4.00 Electronegativity Figure 5. Three-bond proton-13C coupling of neopentyl-1-13C compounds versus substituent electronegativity. Fig 18 59 6.50-—— (:> (CHs)3C13COX 58 6.00... (:> .: :3 ‘5 0') d . 26 54 ° 0 O 5 4 50-—— 29 U .9 O 5' 27 28 5.50 I] l 2.00 2.50 5.00 5.50 4.00 Electronegativity Figure 6. Three-bond proton-13C coupling of trimethyl- acetyl (13C=O) compounds versus substituent electronegativity. 18a Electronegativity references for figures 4, 5, and 6 Number (see Table II) Group Reference 1 H 105 4 CH2Br 106 5 C02H 107 6 OH 107 7 OAC 108 9 02CC5H5 109 11 OTs 108 12 0802 108 14 OSi 105 16 Cl 107 17 Br 107 18 I 107 26 H 105 27 CH3 5 28 C(CH3)3 5 29 OH 107 51 OCH3 110 54 OCSHS 110 56 NHg 107 58 Cl 107 59 Br 107 19 bear out this prediction. The contribution of electronega- tivity can be readily masked by the effects of other factors. Possible factors which cause this non first-order dependence of on s—Character might be: J13CCCH (A) Dihedral Angle. - Although the dependence of J13CCCH on ¢(III) has yet to be experimentally demonstrated, it is ¢ 13C H\£;i:§3/,H III IV reasonable to assume that the relation between J and HCCH ¢(IV) (29) qualitatively applies to J13CCCH and C(III). Any variation in the present data, however, as a result of such dependence can be readily discounted. First, it is highly improbable that any of the compounds examined exists in conformations other than V. Second, even if extreme conform- ational differences (ranging from V to VI) existed between the 13C HtSC H H CH H CH3 CH3 H CH3 H v VI various compounds, the experimentally determined constants should be independent of conformation. Consider JHCCH of a 20 mafiamsoo UnthOuOHm cconiomunu.mmmum> mCHHmeO O O.mmd .mccsomfiou Ooaldlamucmmomc mo .cououm UCOQIOCO mud... 1.n.o.oo_monao o.oma o-mea o.oea o.mma o.oma o.mmd .5 muzmflm _ _ _ _ N mum” ma xww HO A movH AOV 53506 Ann“: O m H _ -m.m loo.m lom.m OO.© tt in 21 CH3CH group as the conformation varies from VII (staggered) to VIII (eclipsed). Using equation 2 (29) one finds that H H H C c VII VIII JHH' = A + BCOS¢ + CCOSZO (2) the average coupling, JHH(avg.) = (JHHa + JHHb + JHHC)/5, is independent of conformation. (B) Angle 9 and 9'. - Vicinal proton-proton couplings, J decrease with increase in angles 9 and 9' (O = < HCC', HCC'H' 9' ; < HC'C) (27,29-55). It is reasonable to assume, there- fore, that J13CCCH might be affected similarly by Changes in e and 9' (9 = < HCC, e' = <13CCC. Although e and e' are not . l 3 H R Ix known for the compounds studied, reasonable guesses can be made as to what structUral features might increase these angles. The most plausible feature is increase in the Size of groups attached to the 13C, e.g., as R increases in size (IX), 6 and 22 9' should increase on account Of nonbonded repulsions. On this assumption several trends and apparent inconsistencies in the data can be qualitatively accounted for. For example, compare the rather large coupling of neopentane (small repul- sions) with the relatively small couplings of all other compounds (large repulsions). Specifically, compare entries (Table II) 1, 19, 21, and 22; 24 and 25; 26, 27, and 28; and 40 and 41. From the low carbonyl stretching frequency of di-t-butyl ketone it was suggested (56) that 9(X) Should be 150-1570. Such an angle requires an s-Character of 0.59- 0.42 for the 13C atomic orbital used in the 13C-C bond. Assuming the 13C atomic orbital of neopentane to have 0.25 s-Character, and using contact interaction, a coupling constant of 7.5-7.8 c.p.s. is calculated for di-t—butyl ketone. The experimental value is only 5.72 c.p.s. It would seem, there- fore, that J13CCCH is extremely sensitive to e and e'. O H C (CH3)3C C(CH3)3 X (C) Bent Bonds. — Theoretical and experimental investi- gations have recently emphasized that the maximum electron density of a sigma-bond may not lie along the internuclear straight line (57-41). Although the effect of bond bending on spin-spin coupling has not been evaluated, it is reasonable to expect that it would decrease contact contribution. With 25 respect to the data discussed, bond bending would introduce the same effects as increases in angles 9 and 9'. The following data seem to be best interpreted if certain bonds are assumed to be bent. From the values (42) of 9(121046') and O'(115O55') of formaldoxime (XI) the lee% R\\3 Pfi?fi!fe:; 1m 3 H/‘e \\OH Hg/ge’ \\OH R \\OH a XI XII XIII s-Characters of the carbon atomic orbitals used in the C-Ha and C-Hb bonds are 0.40 and 0.51. J13CH should therefore be a larger than J13CHb by about 50%. Yet, from XII and XIII, J13CHa (162 c.p.s.) < J13CHb (174 c.p.s.) (45). The assump- tion is made that 9(XII) > 9' (XIII). Similarly, for vinyl Chloride (XIV) J13CH (160 c.p.s.) < J13CH (161 c.p.s.) ,a b although, based on the 0.54 and 0.52 s-Characters (9 = 12101' and 9' = 1190 52') (45) of the carbon atomic orbitals used in the C-Ha and C-Hb bonds, should be greater than JISCHa by about 6%. Smaller J13CHb values have been also Ob- J13CHb served for XV, J13CHa = 156 c.p.s. and J13CHb = 178 c.p.s. (46). The above results can be satisfactorily rationalized if, as a result of nonbonded repulsions, the C-Ha bond is assumed to be bent. In addition to decreasing J13CHa such bending should lead to internuclear 9 values that are larger than the inter- hybrid ones. In the course of this work proton-13C coupling constants were measured for styrene (XVI), acetone oxime b1 24 (XVII), and acetone 2,4-dinitrophenylhydrazone (XVIII) (see Table IV). 6' H H Hb\fg E C: [4me : N Hb\13c : c/ Hal/‘16} Cl Ha/ \C(CH3)2CH2C(CH3)3 Ha/ \CeHs XIV xv XVI b CH b ( ) 3 EL ( ) CH3‘T3 ._ 3C —-N C —-N (a) £13 *9} \OH (a) CH3/ \NHC6H3(N02)2-2,4 XVII XVIII Consistent with the bent bond concept are several long- range proton-13C couplings. From 9(1510) and O'(115O) of acetoxime (47) (XVII) and s-Characters Of the 13C atomic orbitals used in the l3C-CH3(a) and lSC-CH3(b) bonds should be 0.42 and 0.21. Consequently, J13CCH should be about a 7.5 c.p.s. and J13CCHb about 5.8 c.p.s. Yet, J13CCHa (6.27 c.p.s.) < J13CCHb (6.76 c.p.s.). Sim1lar values, J13CCHa (5.90 c.p.s.) < J13CC (7.04 c.p.s.), are obtained for XVIII. Hb These results can again be rationalized by assuming that the l3C-CH3 bonds are bent in the direction shown in XVII. Table IV summarizes a few more long-range proton-13C couplings that are consistent with the concept of bent bonds; e.g., as the nonbonded repulsions between alkyl groups in- crease the coupling decreases. 25 Table IV. Proton-13C Couplings of Various Compounds Compound J13C-CH3 J13C-C-CH3 (c.p.s.) (c.p.s.) 1. (CH3)3C13CH20H 4.48 2. (CH3)313COH 4.25 5. [(CH3)3C]313COH 5.80 4. (CH3)3C13C(CH3)2OH 5.94 5.59 5. (CH3)3C13CHO 4.60 6. (CH3)3C13C(CH3)=O 5.76 4.20 7. (CH3)213C=O 5.90 8. [(CH3)3c]213C=O 5.72 9. (CH3)213C=NOH syn 6.27 anti 6.76 10. (CH3)213C=NNHC6H3(N02)2-2,4 syn 5.90 anti 7.04 EXPERIMENTAL Acetoxime (13C=N) (48) TO 0.50 9. (0.0086 mole) of acetone was added 2.09 g. (0.050 mole) of hydroxylamine hydrochloride in 6 m1. of water and 1.40 g. (0.025 mole) of potassium hydroxide in 4 ml. of water. The mixture was heated on a steam bath for 10 min., cooled, saturated with sodium Chloride, and ex- tracted with three 50 ml. portions of ether. The ether was dried over anhydrous magnesium sulfate, filtered, and fractionally distilled. The remaining acetoxime was sub- limed. Yield: 0.49 g. (77.8%); m.p. 61°. Acetone-2,4-dinitrOphenylhydrazone (13C=N) To a solution of 2,4—dinitrophenylhydrazine reagent (49) was added 5 drOps of acetone. The resulting solid was washed with cold ethanol and vacuum dried. 2,4-Dinitrophenylhydrazine reagent To 0.4 g. of 2,4-dinitrophenylhydrazine in a 25 ml. Erlenmeyer flask was added 2 ml. of concentrated sulfuric acid. Water (5 ml.) was added dropwise, with swirling until solution was complete. To this warm solution was added 10 ml. of 95% ethanol (49). 26 27 thutylmethyl ketone (13C=O) To a 1 ml. Carbon tetrachloride solution of 2,5,5— trimethyl-2-13C-butene-1, prepared in a previous experiment, was added 15 ml. of methylene Chloride. The solution was cooled to -500 and ozone was bubbled in until a blue solu- tion persisted for 5 min. The solution was hydrolyzed with a small amount of 50% hydrogen peroxide and 5% hydrochloric acid. The methylene chloride solution was dried over anhy— drous magnesium sulfate, filtered, and fractionally dis— tilled. The small amount of ketone remaining was pulled over under vacuum (1 mm of Hg) into a trap cooled in liquid nitrogen. EfButyl methyl ketone-2,4-dinitrophenyl— hydrazone (13C=N) To a portion of 2,4-dinitrophenylhydrazine reagent (49) solution were added a few drops of the tfibutyl methyl ketone (13C=O). The precipitate was filtered, washed with cold ethanol and vacuum dried. Acetic acid-1-13C To 24.51 g. (1.00 mole) of magnesium metal in 600 ml. of ether was added dropwise 118.5 g. (0.85 mole) of methyl iodide with a crystal of iodine to initiate the reaction. After forming the Grignard reagent at 00, carbon dioxide—13c (50% enriched) was bubbled into it at 00. The carbon dioxide was generated by dropping 156.8 g. (1.56 moles) of 70% 28 perchloric acid on 107.6 g. (0.545 mole) of 50% enriched 13C. The reaction mixture was warmed to barium carbonate- room temperature, hydrolyzed with 10% hydrochloric acid, saturated with sodium Chloride, dried over anhydrous magnesium sulfate, and distilled. Yield: 20.15 g. (61.4%). Acetamide (13C=O) To 5 drops of acetyl-1-13C bromide was added excess concentrated ammonium hydroxide. The aqueous solution was used as such. Acetyl—l-lsc bromide (50) To 2.0 g. (0.054 mole) of acetic-1-13C acid was added 9.2 g. (0.054 mole) of phosphorus tribromide. After heating for 1 hr. on a steam bath and cooling, the top layer was removed and used as such. Acetyl-1—13C chloride See acetyl-l—lec bromide for procedure. Phosphorus trichloride and a 0.058 mole quantity of acetic acid were used. Acetyl-1-13C iodide A mixture of 2.02 g. (0.054 mole) of acetic-1-13C acid and 4.60 g. (0.011 mole) of phosphorus triiodide (51) was heated on a steam bath for 1 hr. After cooling, the top layer contained 45% iodide and 55% acid. The mixture was used as such. 29 Phenyl acetate (13C=O) To 0.25 9. (0.0052 mole) of acetyl—1-13C Chloride was added 0.50 g. (0.0052 mole) of phenol. The mixture was heated on a steam bath for 1 hr., extracted with 25 ml. of ether, washed with 10% sodium carbonate solution, dried over anhydrous magnesium sulfate, filtered, and the ether evaporated on a steam bath. The remaining acetate was used without further purification. EyMethoxyphenyl acetate (13C=O) See phenyl acetate (13C=O) for procedure. The same mole quantities were used. prNitrophenyl acetate (13C=O) See phenyl acetate (13C=O) for procedure. The same mole quantities were used. N-Phenylacetamide (13C=O) See phenyl acetate (13C=O) for procedure. Aniline and the same mole quantities were used. trButyl alcohol (13COH) To 10.15 g. (0.17 mole) of acetic acid-1-13C in 100 ml. of ether was added 520 ml. of ether solution of diazomethane (52) prepared from 52.6 g. (0.516 mole) of N-methyl—N—nitroso- urea. After drying with anhydrous magnesium sulfate. this solution was added to a solution of methyl magnesium iodide prepared from 12.5 g. (0.51 mole) of magnesium metal 50 and 72.0 g. (0.507 mole) of methyl iodide. One liter of ether was used to make the Grignard reagent. The reaction mixture was hydrolyzed with 81 ml. of an aqueous saturated ammonium chloride solution. After drying with anhydrous magnesium sulfate the ether and alcohol were separated by fractional distillation. Methyl acetate-1-13C See tfbutyl alcohol (13COH) for procedure. Alkyl and aryl acetates (13C=O) The following acetates were prepared by adding a slight excess of the alcohol to a few drops of acetyl-1-13C chloride and warming at 500 for fi-hr.: ethyl, 2-propyl, neopentyl, benzyl, and diet—butylcarbinyl. The reaction mixtures were cooled and used as such. 2,5,5-Trimethyl-2—l3C-butene-1 To 0.80 9. (0.0069 mole) of 2,5,5-trimethyl-2-butanol- 2—13C was added 5.4 g. (0.0045 mole) of oxalyl chloride and 10 ml. of quinoline. To the oil-bath heated vessel was attached a trap cooled in liquid nitrogen. By heating to 1500 all of the olefin formed was caught in the cold trap. It was taken up in 1 ml. of carbon tetrachloride and used as such. 2,5,5-Trimethyl-2-butanol-2—13C To 4.26 g. (0.05 mole) of methyl iodide in 100 ml. of ether was added 0.75 g. (0.05 mole) of magnesium turnings 51 at room temperature. After the Grignard reagent was formed, it was added to 1.04 g. (0.009 mole) of methyl trimethyl- acetate-1-13C in 250 ml. of ether. The reaction mixture was hydrolyzed with 10 ml. of saturated ammonium chloride solution. The ether was decanted from the solid, the solid was washed three times with 50 ml. portions of ether, and the ether solutions were combined and dried over anhydrous magnesium sulfate. Fractional distillation gave 0.80 g. (77.0%) of the alcohol. teButyl iodide (l3C-I) To 0.5 ml. of tfbutyl alcohol (l3COH) was added 5 ml. Of 47% hydroiodic acid. The mixture was heated on a steam bath for 5 min. and cooled. The upper layer was dried over anhydrous potassium carbonate and used as such. Neopentane (-13CH) To 1.00 9. (0.0065 mole) Of neOpentyl-l—lsc bromide in 25 ml. of tetrahydrofuran was added 0.16 9. (0.0065 mole) Of magnesium turnings. By initiating with an iodine crystal and heating to 500 the Grignard reagent was formed. Addition of a small amount of 5% sulfuric acid dissolved all the solids. The mixture was fractionally distilled with only the first milliliter being collected in a liquid nitrogen cooled trap and added to 1 ml. of carbon tetrachloride. The solution was stored in a sealed ampoule. I?“ la. m Th an 52 5,5-Dimethylbutanol-1,1fg2-2-13C To 1.87 g. (0.045 mole) of lithium aluminum deuteride in 200 ml. of ether was added 5.50 g. (0.052 mole) of 5,5— dimethylbutyric-2-13C acid in 100 ml. of ether at 00. After refluxing for 1 hr. the reaction mixture was hydro- lyzed with 6 ml. of 5% sulfuric acid. The ether was decanted off, dried over anhydrous magnesium sulfate, filtered, and fractionally distilled. Yield: 2.92 g. (91%). 5,5-Dimethylbutyl-1,1-d2-2-13C acetate To 1.00 9. (0.0096 mole) of 5,5-dimethy1butanol-1,1- g2-2—13C was added 0.79 g. (0.01 mole) of acetyl Chloride. The mixture was heated on a steam bath for 1 hr., cooled, and used as such. 5,5—nimethylbutyl-1,1-g2-2-13c bromide To 0.69 g. (0.0066 mole) of 5,5-dimethy1butanol—1,1- g2-2-13C in 5 ml. of benzene was added 0.60 9. (0.0022 mole) of phosphorus tribromide in 5 ml. of benzene. The mixture was refluxed for 1 hr., the benzene layer was washed with water, dried over anhydrous magnesium sulfate, filtered, and fractionally distilled. The remaining material contain- ing some benzene was taken up in carbon tetrachloride and used as such. 5,5-Dimethylbutyric—2-13C acid To 6.10 g. (0.040 mole) of neopentyl—1-13C bromide in 500 ml. of ether was added 1.08 g. (0.045 mole) of magnesium 55 metal. After formation of the Grignard reagent at room temperature, anhydrous carbon dioxide was bubbled in until reaction ceased. All solid material was dissolved with concentrated hydrochloric acid. The ether was removed, dried over anhydrous magnesium sulfate, filtered and frac- tionally distilled. Yield: 5.50 g. (71.5%). See PART II EXPERIMENTAL for the following compounds: Trimethylacetic-1-13C acid Neopentyl-1-13C alcohol Neopentyl-1-13C tosylate Neopentyl-1-13C iodide Neopentyl-1-13C chloride Neopentyl-l-lsc-ammonium perchlorate Trimethylacetamide-1-13C Trimethylacetonitrile-1-13C Difitfbutylketone (see trimethylacetic—1-13C acid) Trifit-butyl carbinol (see trimethylacetic-1-13C acid) Neopentyl—1-13C acetate To 0.50 9. (0.0057 mole) of neopentyl-1-13C alcohol was added 0.42 9. (0.0057 mole) of acetyl Chloride. The mixture was refluxed on a steam bath for 1 hr., dissolved in 50 ml. of ether, and washed with 10% sodium carbonate solution. The ether was dried over anhydrous magnesium sulfate, filtered, and fractionally distilled from the 54 acetate. The acetate was collected under vacuum (1 mm.) in a trap cooled in liquid nitrogen. Yield: 0.50 g. (68.0%). Neopentyl-1—13Cpggmethoxybenzoate To 0.50 9. (0.0057 mole) of neopentyl alcohol was added 0.97 9. (0.0056 mole) of freshly distilled pfmethoxybenzoyl chloride, b.p. 105-1070 (1 mm.). The mixture was heated on a steam bath for 1 hr., cooled, dissolved in ether and washed with 10% sodium carbonate solution. The ether solu- tion was dried over anhydrous magnesium sulfate, filtered, and evaporated on a steam bath. The resulting oil was dis— tilled under vacuum (1 mm.) in a Short-path apparatus. Neopentyl-1-13C benzoate To 0.50 g. (0.0057 mole) of neOpentyl alcohol was added 0.80 9. (0.0057 mole) of benzoylchloride. The mixture was heated for 2 hrs. on a steam bath, cooled, taken up into carbon tetrachloride, and used as such. Neopentyl-1-13C Ernitrobenzoate To 0.50 9. (0.0057 mole) of neopentyl alcohol was added 1.05 9. (0.0057 mole) of Ernitrobenzoyl Chloride. The mix- ture was heated on a steam bath for 24 hrs., cooled, and crystallized from ethanol. M.p.: 54o. Neopentyl-1-13C sulfite (55) To 0.50 9. (0.0057 mole) of neopentyl alcohol and 0.45 9. (0.0057 mole) of pyridine in 2.0 ml. of ether was added 55 dropwise at -150 0.54 9. (0.0028 mole) of thionyl chloride in 1.5 ml. of ether. The reaction mixture was warmed to room temperature, washed with water, dried with anhydrous magnesium sulfate, filtered and fractionally distilled. The remaining sulfite was used as such. Neopentyl—1-13C Chlorosulfite (55) To 0.50 9. (0.0057 mole) of neopentyl alcohol in 1.5 ml. of ether was added drOpwise at -150 1.07 g. (0.009 mole) of thionyl chloride. The reaction mixture was warmed to 700 over a 1 hr. period, cooled, and fractionally distilled. The remaining Chlorosulfite was used without further purifi- cation. Neopentyl-1-13C trimethylsilyl ether (54) To 0.50 9. (0.0057 mole) of neopentyl—1-13C alcohol was added 0.62 9. (0.0057 mole) of trimethylsilyl Chloride and 0.45 g. (0.0057 mole) of pyridine. The reaction mixture was heated on a steam bath for-é hr., cooled, taken up into 50 ml. of ether, and washed with 10% sodium carbonate and 5% hydrochloric acid. The ether was then dried over anhydrous magnesium sulfate, filtered, and fractionally distilled. The remaining silyl ether was used as such. Neopentyl-1-13C bromide To 10.66 g. (0.12 mole) of neopentyl-1-13C alcohol was added 20.60 g. (0.12 mole) of benzyl bromide and 57.50 g. (0.12 mole) of triphenylphosphite. The mixture was kept at 56 1400 for 46 hrs. After cooling, the mixture was vacuum dis- tilled into a trap cooled in liquid nitrogen. The product was taken up into 250 ml. of ether, washed with 10% sodium hydroxide, dried over anhydrous magnesium sulfate, filtered, and fractionally distilled. No yield was recorded. Dietebutylcarbinol (l3CHOH) To 0.58 g. (0.01 mole) of lithium aluminum hydride in 25 ml. of ether was added dropwise, at 00, 0.26 g. (0.0018 mole) of dietfbutyl ketone in 25 ml. of ether. The reaction mixture was heated to reflux for 1 hr., cooled, and hydro- lyzed with 5% sulfuric acid. The ether solution was dried over anhydrous magnesium sulfate, filtered, and fractionally distilled. The remaining alcohol was purified by v.p.c. on the 10 ft. Carbowax 20M column. Difitfbutylcarbinyl acetate (l3C-O-g) To a few drops of acetyl Chloride were added a few drops of dijt—butylcarbinol (13COH). After warming at 500 for a few minutes, the reaction mixture was cooled and used as such. 9 Trijt-butylcarbinyl acetate (lac—O-C) This compound was prepared in the same way as the diet: butylcarbinyl acetate (l3C-O-g). tfiButylethylene-1e13C-2,2-d2 To 1.4 g. (0.0096 mole) of 5,5-dimethylbutyl-1,1-g2-2-13C acetate was added 25 ml. of benzene. This mixture was 57 percolated through a glass helices packed column heated at 5000. The bottom of the column was connected to a one- necked S 24/40 500 ml. round-bottomed flask which was cooled in liquid nitrogen. After the product and benzene were collected and transferred to a small fractional distillation set-up, the olefin was distilled off from the benzene. A small amount was obtained and was taken up in carbon tetra- Chloride. Trimethylacetaldehyde (13C=O) (55) Dry nitrogen gas was slowly passed (15 CC./min.) over 2 g. of neopentyl alcohol entraining it into a 10 in. x 5/4 in. I.D. Vycor tube. The tube was tightly packed with copper turnings and placed in a tube furnace at 5150. The resulting aldehyde was entrained into a trap cooled in liquid nitrogen. A 100% yield of aldehyde was obtained. Methyl trimethylacetate-1-13C To 1.00 g. (0.01 mole) of trimethyl-1-13C acid in 10 ml. of ether was added a 100 ml. ether solution of diazomethane (52) prepared from 2.06 g. (0.02 mole) of N-methyl-N-nitroso- urea. The ether was dried over anhydrous magnesium sulfate, filtered, and fractionally distilled. The remaining ester was used as such. Neopentyl trimethylacetate (13C=O) To 0.5 g. (0.0041 mole) of trimethylacetyl-1-13C Chloride was added 0.56 g. (0.0041 mole) of neopentyl alcohol. 58 The mixture was heated on a steam bath for 1 hr. and cooled. The material was used without further purification. Phenyl trimethylacetate (13C=O) To 0.16 g. (0.001 mole) of trimethylacetyl bromide (13C=O) was added 0.09 g. (0.001 mole) of phenol. The mix- ture was heated on a steam bath for 1 hr., taken up into carbon tetrachloride, and used as such. prMethoxyphenyl trimethylacetate (13C=O) The same procedure and mole amounts were used as in the synthesis of phenyl trimethylacetate (13C=O). prNitrophenyltrimethylacetate (13C=O) The same procedure and mole amounts were used as in the synthesis of phenyl trimethylacetate (13C=O). N-Phenyl trimethylacetamide-1-13C To 0.10 9. (0.00085 mole) of trimethylacetyl—1—13C Chloride was added 0.16 9. (0.0017 mole) Of aniline. The mixture was heated on a steam bath for 5 min., cooled, ex- tracted with ether and washed with water. The ether was dried with anhydrous magnesium sulfate, filtered, and re— moved on a steam bath. The resulting solidwas used as such. Trimethylacetyl Chloride (13C=O) To 1.04 g. (0.01 mole) of trimethyl acetic acid was added 1.55 g. (0.01 mole) of thionyl chloride. The reaction 59 mixture was heated on a steam bath for 1 hr., cooled, and used without further purification. Trimethylacetyl bromide (13C=O) To 0.77 9. (0.0075 mole) Of trimethylacetic acid was added 0.68 9. (0.0025 mole) of phosphorus tribromide. After heating on a steam bath for 1 hr., the reaction mixture was extracted with ether and the ether was fractionally distilled. The remaining acid bromide was used as such. Trimethylacetaldehyde-2,4—dinitrophenyl- hydrazone (13C=N) (49,56) To a solution Of 2,4-dinitrophenylhydrazine reagent were added 5 drops of trimethylacetaldehyde. The resulting solid was washed with some cold ethanol and vacuum dried. PART II CARBONIUM ION REARRANGEMENTS IN THE n-PROPYL AND NEOPENTYL SYSTEMS 40 INTRODUCTION In reactions which are known to generate carbonium ions the neopentyl system always gives products resulting from the t-amyl cation. The deamination of the amine (57,58), solvolysis of the tosylate (57-59), solvolysis of the Chloride (58) and iodide (60), deoxidation of the alcohol (57), and bromination of the alcohol with hydrobromic acid (61) all lead to t-amyl products and iso-pentenes. Thus, it appears that in the neopentyl system, the Wagner-Meerwein rearrangement leading to a tertiary cation from a primary one is completely favored over nucleophilic attack on the primary cation. It has been suggested (59,62-68) that many carbonium ion rearrangements proceed by way of methyl-bridged non- classical carbonium ions (I). Protonated cyclopropane inter— mediates (57,69-72) (II) have also been postulated since \/ /F§3 ///p H / \ , e x. X —--C/ """ l’:-— —-—C 6’ C— / I \ / II \ cycloprOpanes are found to be products of many Of these reactions (5%,62,68,75,74). The intermediacy of protonated cyclopropanes in gas-phase ionic decompositions in the mass 41 42 spectrometer is well documented (72,75,76). The suggestion that such species may intervene as intermediates in liquid- phase carbonium ion rearrangements, however, has not been substantiated. Evidence for methyl-bridged non-classical carbonium ions (64,67,68) and protonated cyclopropanes (70-72) has been none too plentiful and evidence against them in many systems (58,61,77,78)has been given. The occurrence of Wagner—Meerwein 1,5-shifts in open- Chain systems has eluded unambiguous confirmation. Such Shifts have been proposed (79-81) in mechanistic interpreta- tions of product formation in carbonium ion reactions, e.g., (1) has been suggested (79). However, the products Can always be rationalized equally well by postulating successive 1,2-shifts, (2). Nevertheless, the reported 1,5-hydride C C C C C I I $1§_5. é I I C—C-c-C-Cv—-— C— -C—C-C (_1_) C + + C C C C C C C 1 2 | l I r l 1,2 3 g: I C-C-C—C—C\——— C- -C—C-C :— C-C—C-C-C (_2_) C+ + + shifts (74,86) and proton exchange betWeen cyclopropane and sulfuric acid (85) might be interpreted in terms of pro- tonated cyclopropanes, either symmetrical (II) or hydrogen bridged (III). 45 In the simplest system where it is possible to generate a methyl-bridged cation or protonated cyclopropane, or have a 1,5-hydride shift occur, the n-propyl system, cycloprOpane is a product in the deamination of the amine (57) and deoxi- dation of the alcohol (57). It has been reported (77,84,85) that the nitrous acid deamination of the perchlorate salt Of n-propylamine-1-14C leads to labeled 1-propanol and 2-propanol, the label in only. 1-propanol being at C—1 and C—5 Solvolysis of cyclopropane in deuterated sulfuric acid (85) leads to 1-propanol containing deuterium at C-1, C—2, and C-5. Treatment same conditions leads to deamination of the amine or successive 1,2-shifts of unlabeled 1-propanol under the no incorporation of the label. The suggests a 1,5-hydride shift (5) (4) whereas the solvolysis of the cyclopropane suggests a protonated cyclopropane (5). CH3 'CH2-1 4CHg _L'5">‘ CHg-CHg-14CH3 O 1 2 CH3 ~CH2 -1 4CH2 —-'-—‘- CH3 -CH-l 4CH3 9 ‘ (5) e ‘_1"—2—L‘ CHg-CHg "'1 4CHg (4) e e .5” :e ~:H————)-etc. (:33) , ,’ *r——-' CH2 44 In the neopentyl system cyclopropanes have never been found (58,61-65,75). However this does not remove the pos— sibility of forming a methyl-bridged non-Classical carbonium ion or protonated cyclopropane intermediate which decom- poses to the tert-amyl Cation. The non—Classical carbonium ion has only two modes of decomposition, one leading to a primary ion and the other to a tertiary ion (6). CHs—lcscha -—9'CH3-lC-2CH2-3CH3, CH3-1C—3CH20 (6) . x e 3EH3 3CH3 If a non-Classical ion is formed it can only be deduced in- directly, by kinetics (67) for example, and not by any direct means such as labeling. If a protonated cyclopropane is formed it has three modes of decomposition (1), one leading CH3 CH3 CH3 CHa-lqg2CH2 -——>-CH3-1C-2CH2-3CH3, CHg-lC-3CH2-2CH3, 37K\\H 6 e 3 H2 CH3 (7) CH3---1 ~2CH26 3 H3 to a primary ion and two leading to tertiary ions. In (6) and (1) the primary ion can be discounted Since no primary product is found. The path of the rearrangement can be elucidated by suitably labeling the neopentyl group and locating the iso— tope in the t-amyl group. Chart I summarizes the isotopic distributions predicted for various paths on the assumption 45 sooe +00 HlUlU .HO xUmHHHU sheen sm.mm + so.oo + w .(r, . Assuoenm a J Oosnonwuo + OnonwuonH .lTuuesn Oosuwno sheen O essuoeum.a +O onenomsum.e AOV w . Inc O H 0 son son + + Onauouwno + 0:02:qu All +m O .O A H BED Adv _ _ U 46 that isotope effects are negligible and that no further scrambling of atoms occurs once the t-amyl structure is attained. Path a, a 1,2-methyl shift, leads to a t-amyl Cation labeled solely at C-5; path b, involving a protonated cyclopropane, distributes the label equally between C—5 and C-4; path C, a single 1,5-hydride shift followed by a 1,2-methyl shift, distributes the label between C-1 and C-4 in a 2:1 ratio. The n-propyl and neopentyl systems were Chosen for study due to their simplicity and absence of interfering groups. The path of decomposition, possibly involving 1,2-hydride shifts, 1,5-hydride shifts and protonated cyclopropanes, to be studied by means of suitably labeled compounds is the sub- ject of this part of the thesis. RESULTS gyPrOpyl System 1-Propylammonium-1,1fig2 perchlorate The 1-propanol obtained from the deamination at 400 of 1-propylammonium-1,15g2 perchlorate (96.6% Q2 and 5.4% Q1) was converted with hexamethyldisilazane to the trimethylsilyl ether. IsotOpiC composition of the silyl ether, calculated from the parent-less-methyl peaks, was 96.4% g2 and 5.6% Q1. The isotopic composition of the amine was obtained from the mass spectral analysis of its diacetamide. Good agreement between the values from the diacetamide and the silyl ether supports the View that methyl loss occurs solely from the trimethylsilyl group and that no deuterium-protium exchange occurs between substrate and solvent during the reaction. The parent-less-ethyl ion of the silyl ether had the compo- sition 91.6% g2, 4.9% g1, and 5.5% 40- These values corres- pond to the isotopic composition of the a-methylene group of the 1-propanol. The mass spectral analysis of the trimethylsilyl ethers of 1-propanol-1,1fig2 prepared from the reduction of propionic anhydride (a and b), prOpionic acid (C) and prOpionyl chloride by lithium aluminum deuteride (d) gave the results summarized in Table I. 47 48 Table I. Mass Spectral Analysis of the Trimethylsilyl Ethers of 1-Propanol-1,15g2 Prepared by Lithium Aluminum Deuteride Reduction Parent-less-methyl Parent-less-ethyl Q2 9.1 Q0 Q2 Q1 9.0 (a) 98.8 1.2 0.0 98.5 1.6 0.1 (b) 99.0 1.0 0.0 98.5 1.6 0.1 (C) 88.4 11.5 0.1 87.7 12.0 0.5 (d) 88.4 11.4 ' 0.2 87.5 12.1 0.4 As can be seen from Table I, the composition of the a—methylene group of the trimethylsilyl ether of the 1-propanol Obtained from the deamination of the 1-pr0pylammonium-1,1egg perchlorate needs to be corrected. On the average, the g; and Q0 intensities of the parent-less-ethyl ions are 0.6% and 0.2% larger and the g; 0.7% smaller than those values ob— tained from the parent-less-methyl ions. This indicates that this much rearrangement is taking place in the mass spectrom- eter-in the Cleavage of the ethyl group. Therefore, the isotopic composition of the a-methylene group of the 1—propanol obtained from the deamination Should be 92.4% d2, 4.5% g1, and 5.5% Q0- Since the parent-less—methyl peaks of the trimethylsilyl ether of the 1-propanol from the deamination shows that there is 5.6% g; amine in our starting material, it must be sub- tracted in order to put our final composition of trimethylsilyl 49 ether on a 100% g2 basis of the starting amine. Since there is about 95% unrearranged alcohol in the reaction, the 5.6% g; amine contributes 5.4% Q; and 0.2% Q0 to the 1—propanol. Subtracting this amount (5.4%gl and 0.2% do) from the tri- methylsilyl ether a composition of 92.4% $2, 0.9% gl, and 5.1% Q0 is arrived at. Putting the composition on a 100% basis yields 95.9% 912, 0.9% g1, and 5.2% do. A second run at 400 gave 1-prOpanOl having a composition of 98.0% g2 and 2.0% g; from the parent-less-methyl ion and 95.6% g2, 5.2% g1, and 5.2% go from the parent—less-ethyl ion. Applying all corrections as before, the 1-propanol becomes 96.5% g2, 0.7% g1, and 5.0% do. A run at 00 gave 1-propanol having a composition of 98.2% g2 and 1.8% gl, from the parent-less-methyl ion and 95.4% Q2, 2.8% g1, and 1.8% Q0 from the parent-less-ethyl ion. Apply- ing all corrections as before, the 1-propanol becomes 98.0% 212. 0.5% 51.1. and 1.5% do. 1-Propy1ammonium-2,2-§2 perchlorate Isotopic analysis of the trimethylsilyl ether of the 1—propanol obtained from the deamination of the perchlorate at 400 gave 98.0% g2 and 2.0% d; from the parent-less-methyl ion and 1.4% 92, 1.1% Q1, and 97.5% do from the parent-less ethyl ion. The silyl ether of authentic 1-prOpanol—2,25g2 gave the following results: 98.4% g2 and 1.6% d; from the parent-less-methyl ion and 0.2% g2, 0.2% Q;, and 99.6% do from the parent-less-ethyl ion. The correction factors for 50 deuterium and protium rearrangement in the mass spectrometer to be added to the parent-less—ethyl isotope analysis Of the 1-propanol from the deamination of the amine are: —0.2% d2, -0.2% g4, and +0.4% do. The parent-less-ethyl peak thus be- comes 1.2% Q2, 0.9% Q1, and 97.9% do. Subtracting out the .Q1 present in the starting material in order to have the analysis on Q2 starting material only, the analysis becomes 1.2% g2, 0.9% Q1, and 96.0% Qo- Putting this on a 100% basis, the final values become 1.2% Q2, 0.9% Q1, and 97.9% go. The results are summarized by (8) and (9). O CH3CH2CD2NH2 '329' C2H5“CD20H + C2H4D-CHDOH + 100% g2 IV, 96.1% v, 0.8% C2H3D2-CH20H VI, 5.1% (g) 400 CH3CD2CH2NH2 ————v- CgHs-CDEOH + C2H4D-CHDOH + 100%g2 IV',-1.2% v', 0.9% CgHng-CHZOH VI', 97.9% (g) The Neopentyl SYstem The t-amyl alcohol Obtained from the deamination of neopentyl-1-13C and neopentyl-1,1—d2-amines, from the sol- volysis of neopentyl-1-13C and neopentyl-1,1—d2 tosylates, 51 and from the solvolysis of neopentyl-1-13C iodide were analyzed by n.m.r. (60 MC.) and mass spectrometry. The t-amyl Chloride obtained from the reaction of neopentyl-1- l3C alcohol with triphenyl phosphite and benzyl chloride was analyzed by n.m.r. The preparation of neopentyl iodide (86,87) (triphenyl phosphite and methyl iodide) yielded no detectable (n.m.r. analysis) rearrangement to t-amyl iodide while the preparation of the chloride gave a 50—50 mixture of neopentyl Chloride and t-amyl Chloride. Isotopic composition of the l3C-labeled neopentyl com- pounds was determined by integration of the -13CH2- and -13CH2-signals. The values, believed to be accurate to i4%, in terms of percent labeled molecules are: neopentyl-1-13C- ammonium perchlorate, 51.5%; neopentyl-1—13C tosylate, 55.8%; neopentyl-1-13C iodide, 54.5%; and neOpentyl-1-13C Chloride, 55.7%. Neopentyl-1,1-d2—ammonium perchlorate and neopentyl- 1,1—d2 tosylate were estimated to be at least 96% d2. Fig. 1 shows typical spectra. The t-amyl alcohols isolated from the rearrangement of the dg-labeled neopentyl compounds showed no protium at C—5 (less than 5%). Those obtained from the l3C-labeled compounds showed no 13C at C-1 or C—4. From integration of the -13CH2-signals at 7.4 versus other signals (OH, -12CH2-) the amount of 13C at C-5 from deamination was estimated to be 50.6%; from tosylate solvolysis, 55.2-57%; and from iodide solvolysis, 55.8%. The t-amyl chloride also showed no l3C 52 umcflxo Edflumusmp CH mumHOHnonmm ESHGOSEOINWVH.Hlamucmmowc mo Esuuommm .H.E.: cououm on“ confirm onO ommmoooo Aomov 55 at C-1 or C-4. Typical spectra are shown in Fig. 2. Apparently all the labeled atoms-deuterium and l3C-in the t-amyl compounds are confined to the C—5 position. TableIEIshows partial spectra of t-amyl alcohols ob- tained from the rearrangement of labeled neopentyl compounds. Analysis (92) of these spectra gives the following results: . + . 13C label in the CsHll lon, parent-less- retention of hydroxyl, is 50, 55, and 54% for the alcohols obtained from the deamination solvolysis of tosylate, and solvolysis of iodide, respectively. Retention of 13C label in the C4H90+ ion, parent-less-methyl, is 29.4, 56.5, and 56.2%; in the C4H7+ ion, parent-less-methyl-and-water, it is 29, 55, and 54%. Hence no label is at C-1. l3C retention in the C3H7O+ ion, parent-less-ethyl, is not more than 0.2, 0.2, and 0.2%. If intensities at masses 74 and 75 in the spectra of the deuterated alcohols are attributed solely to C4H90+-d1 and —d2, respectively, and if unlabeled C4H90+ is assumed absent, an estimate can be made of the isotopic distribution of this fragment-ion and, by inference, of the parent molecule: 5.6% d; and 96.4% d2 in both alcohols. Deuterium retention in the C3H7O+ ion is essentially zero. All the 13C and deuterium, therefore, is confined to the ethyl groups. The n.m.r. and mass spectral data are in good agreement, and the combination of the two leads to the conclusion that all label originally at C—1 of the neopentyl compounds ends up at C-5 of the t-amyl compounds. Table III summarizes the results. 54 OH _ (CH3)at-C02—CH3 -OH 1:; I ’T’: 6.08 Fig. 2a. Proton n.m.r. spectrum in carbon tetrachloride of tramyl alcohol obtained from the deamination of neopentyl-1,ljgg-ammpnium perchlorate. ?H (CH3)2CCH2CH3 ’l’: 5.97 7.0 Fig. 2b. Proton n.m.r. spectrum in carbon tetrachloride of tramyl alcohol obtained from the solvolysis of neopentyl-1-13C tosylate. 55 Table II. Partial Mass Spectra of t-Amyl Alcohols Relative Intensitya Mass Ib IIC IIId Ivb ve VIf VIIg 55 5.10 2.55 1.62 5.84 2.06 1.09 1.09 54 0.60 1.24 1.82 0.74 2.58 1.85 1.84 55 41.6 29.1 18.4 47.8 22.1 5.19 5.16 56 0.47 11.8 22.4 0.41 26.0 11.1 11.5 57 2.62 2.20 1.68 2.75 1.64 56.0 56.5 58 1.82 2.28 2.45 1.76 2.55 2.15 2.12 59 100.0 100.0 100.0 100.0 100.0 100.0 100.0 60 0.10 0.24 0.20 0.05 0.18 2.27 2.29 61 0.12 0.09 0.08 0.17 0.15 0.10 0.11 69 0.81 0.69 0.59 1.01 0.47 0.17 0.17 70 5.80 2.65 1.96 5.87 5.04 0.45 0.41 71 5.46 4.97 4.57 5.62 5.61 2.24 2.25 72 0.20 1.85 5.22 0.14 5.16 5.58 5.65 75 55.6 59.1 24.4 55.5 24.6 5.66 5.62 74 0.07 16.5 51.4 0.05 51.6 2.14 2.14 75 0.0 0.0 0.0 0.0 0.0 57.9 57.5 76 0.0 0.0 0.0 0.0 0.0 0.79 0.80 a I I O I I O O ' Contributions from ions containing heavy isotopes in natural abundance have been removed. Unlabeled. b spectra, the same C From 0.: From (D From From 9From the the the the the I and IV, Spectrum I was measured at the same time as II and III, time as V, VI, and VII. deamination of neopentyl-1- 13C The spectra shown here Hence two -amine. solvolysis of neopentyl-1-13C tosylate. solvolysis of neopentyl-1-13C iodide. deamination of neopentyl-1,1-d2 amine. solvolysis of neopentyl-1,1-d2 tosylate. Interpretation of spectra of labeled compounds requires comparison with spectra of the corresponding unlabeled species measured consecutively or nearly so to ensure constant instrument Operating characteristics. were measured in two groups at different times. are reported for the unlabeled alcohol. IV at fl 4.: : lam .mo .uomo . . 0 Ho m mg .Esnuommm .H.E.G may Eoum coumHsOHmom oomA unconsom coaoooaxooo memoounfinmov ooaeoun assenu umm nomA + nmcouoom sues coeuomom mommOoaOnxanv HommOnmoO + moAOnmoOV % mmmA OUHMOHQU H>Eeaom HmmOnaOnxomOv 0 cos ... o Honooam Hmseuu mammao>aom uBOmQOOnAanV o cos c o Hosooam smears namsao>aon neonmonaOoxnmov o ooa ... o Hosooam Hagen» coeumceemoo nsOHOnm+2moOOnxomOV o 005 o o Hocooam assets coaumcaemoo usoHOnm+2mmOnsOoxanV filo mlo. NIU HID uospoum COHuomom UCDOQEOO Hmucmmooz unmoumm .mpcsomEOO HSEMIU Cw Henna mpcsomEOO HaqumOOz mo Dawsomcmuummm mnu Eoum Conflmuno mccsomeoo H>E- CH3CDCH2D —L CH3CHDCHD “—"— V—— vl (19) ~13 + NH + CH CH CD —'~ CH CHCHD 3 2 2 V—‘_—' 3 2 IV' 2-Aminopropane has been shown to yield no 1-propanol. This too helps to rule out reversible 1,2-shifts. 1,5—Shifts can be ruled out on the basis that 1-aminopropane-2,2—§2 57 58 forms 1-propanol with label in the 1-position. Since [V]=[V'], 1-aminopropane-1,1eg2 and 1-aminopropane-2,2jd2 must lead to the same isotope position intermediate, or its equivalent, prior to the formation of isotopically rearranged 1-propanol. This intermediate (Chart II) accommodates the results, pro- vided the following are true: (a) from [V]= [V'], VII;::§ VII' is much faster than reaction of these ions with solvent to form 1-propanol. In terms Of isotope position rearrange- ment, this is indistinguishable from a symmetrical protonated cyclopropane. [b] From [IV'] > [V'], VII :2: VIII is slower than VII :::”VII' and competitive with reaction of the ions with solvent. Mechanism I is therefore ruled out, because it requires assumptions already excluded by solvolytic studies of cyclopropane in deuteriosulfuric acid (88,89). Mechanism II (Chart III), either A or B, is consistent with the results and those of Baird and Aboderin (88,89). For path A to be correct, X must go to VII and VII' as fast as or faster than it reacts with solvent to give 1—propanol. For path B (formation of VII and VII' without the interven- tion of X) to be correct, VII and VII' must arise in the same ratio from either labeled species. Neither path requires the excluded (88,89) condition that VII :;j7VIII be slower than VII : VII' . In conclusion, the results indicate that at 400 about 5% (1.2% IV, 0.9% V, and 5.2% VI) of the 1—propanol arises from protonated cyclopropanes and 95% from an intermediate, or Tali. -. l. +mmONOOomO m .Oum .HH> \\ NNEUNDUMSO Q fi f NQ) N N\mU HHH> haw nnnnnnn +moOmmOan / + \\\ / .HO / \ mumnvx m I: .ILV .ILV d .Ouo_AII.HHH>.4II HH> NmoOmmOan .HH> + HH> HHH em .HH> m .omo («To \.mm m m n \\\.\ “/ \\\ "/ \\\ u/ .7 mo no EU m, + . GEO :Allll Q, + " \\\@30 m/ + _ moo .Alllll no I/ — // // x, . _ / _ mm mounmo mmO\\\\ Ime\ mmO N O xH HHH> a HH> mgfi omO omO \ob///, moOmmOomO \ \\\ _/ \\ \\ _/ \\ n + m, + " mmO All: 0, + " mmO All 3. + .\NTO AIIIII no I / I/ _ , _ x/ _ x _ NcummOan zomO\\\\\ mmO\\\\\ mmO N HH Bm' C-C-C-C + (t.s.) (19) extremes can also be visualized. The relative merits of 10a and 10b in terms of X have been recently discussed (58,94). In most cases the available data bar a choice between the two mechanisms. Path 10b apparently intervenes in the reaction of neopentyl iodide with silver nitrate. In this case optically active neopentyl-l-d iodide leads to inactive t-amyl alcohol (94). Path 10a has been implicated (94) in the deoxidation of neopentyl alcohol, because optically active (presumably inverted) 2-methy1-1-butene-5—d results from optically active neopentyl-1—d alcohol. The results, however, are equally compatible with path 10b pro- vided the methyl rearrangement (11a) is faster than or competes favorably with rotation of-the -CHD group with H D CH3 + \ D CH3 + H CH3" ‘x' -;;2> CH *“ 5i" CH3 CH3 respect to X (11b). These differences in the behavior of 65 neopentyl Cations may reflect the importance of X in product control rather than a change from a two—step to a concerted mechanism. vibrationally excited neopentyl Cations, e.g., those formed from deamination and deoxidation, may underto rearrangement faster than rotation about the -C+HD group with respect to X. Recent publications have focused atten- tion on the importance of counter ion X and solvent in the competition between product formation and conformational changes of carbonium ions (95,96). EXPERIMENTAL Purification of liquid products The propanols, the Efamyl alcohols, the trimethylsilyl ethers, and the diacetamides were all purified for mass spectral and n.m.r. analysis by vapor phase Chromatography, by using a 10 ft. x i-in. 20% Carbowax 20M on 60/80 Chromo- sorb W column for the alcohols and ethers and a 6 ft. x i-in. 20% Carbowax 20M on 60/80 Chromosorb W column for the diacetamides. The alcohols were run at about 800, the ethers at 500, and the diacetamides at 155°. An Aerograph A-90-P gas chromatograph was used. The Eramyl chloride and neopentyl Chloride were separated by vapor phase Chromatography using a 7 ft. x i-in. 15% Bentone 54 and 5% SE-52 On 60/80 Chromosorb W column at 700. Fifty to seventy microliter injections were used in all cases . Preparation of trimethylsilyl ethers (97) By using small glassware (S 14/20), 0.1 to 0.5 g. of the alcohol was refluxed on a steam bath for two hrs. with one-half the molar amount of hexamethyldisilazane and one drop of trimethylsilyl chloride. The cooled reaCtion mixture was used directly for VPC purification and then mass spectral analysis. 64 l A 65 1-Propyl- LN-diacetamide (98) To 5.0 g. (0.02 mole) of the perchlorate salt of the amine was added 5.6 g. (0.1 mole) of potassium hydroxide and 15 ml. of water. The solution was immediately distilled (the amine comes over first) into 10 ml. of toluene. The toluene was dried with anhydrous magnesium sulfate. To the toluene solution was then added 5.1 g. (0.04 mole) of acetyl Chloride and 5.17 g. (0.04 mole) of pyridine in 10 m1. of r755 I toluene. The mixture was refluxed on a steam bath for 1 hr., cooled, washed with three 25 ml. portions of water, dried, and distilled. The remaining diacetamide was purified by VPC. 1-Propyl-N,N-diacetamide-1,1fig2 The same procedure as for the unlabeled amine was used. A 0.019 mole quantity of starting material was used. 1-Propanol-1,11Q2 To 6.20 g. (0.048 mole) Of propionic anhydride in 25 ml. of dry ether was added, at 00, 2.00 g. (0.048 mole) of lithium aluminum deuteride in 100 ml. of ether. The mixture was warmed to room temperature slowly and then refluxed on a steam bath for 5 hrs. After cooling, 4 ml. of water and 4 m1. of 5% sodium hydroxide solution were added. The ether layer was decanted, dried over anhydrous magnesium sulfate, and fractionally distilled. Yield: 5.02 g. (51.0%). 66 1-Propylammonium-2,21gg perchlorate To 15.50 g. (0.55 mole) of lithium aluminum hydride in 250 ml. of ether was added dropwise 14.24 g. (0.25 mole) of propionitrile-d,a-d2 in 50 ml. of ether. The mixture was refluxed on a steam bath for 5 hrs., cooled, worked pp with 100 ml. of water, and distilled into 55.8 g. (0.25 mole) of 70% perchloric acid. The ether, water, and perchloric acid were removed under vacuum. The remaining solid was crystal- lized (84) from p-heptyl alcohol and pfpentane. Yield: 25.75 g. (75.2%) . 1-Propylammonium-1,1fi§2 perchlorate The procedure used was exactly the same as that for the 1-propylammonium-2,2:d2 perchlorate. A 0.2 mole quantity of starting materials was used. Methylmalonic acid (99) Shake 149.8 g. (0.86 mole) of methylmalonic acid diethyl ester with 10 g. of sodium hydroxide in 50 ml. of water at 00 for one minute to remove any malonic acid diethyl ester present. Wash once with 100 ml. of water. Add to the ester in a 5—necked S 24/40 1 liter round-bottomed flask equipped with a condenser, stirrer, and thermometer 157.6 g. (5.44 mole) of sodium hydroxide in 400 ml. of cold water. Heat with stirring on a steam bath to 800 and maintain for 1 hr. Cool, extract three times with 100 ml. portions of ether, make acidic (pH < 1) with cold concentrated hydrochloric 67 acid and extract with three 100 ml. portions of ether and salt out with sodium chloride. Dry the ether solution with anhydrous magnesium sulfate, filter, and remove the ether under vacuum using a warm water bath (50°). The yield after one crystallization from ethyl acetate was 65.1 g. (72.8%). Methylmalonic aCid-afgfcaerXYIfgg (100) Fifty g. of methylmalonic acid was dissolved in 100 ml. of deuterium oxide in a stoppered 250 ml. 1-neck S 24/40 round-bottomed flask and kept at 550 for 18 hrs. After remov- ing the water by heating to 550 under vacuum, another 100 ml. of deuterium oxide was added. After a total of eight exchanges, approximately 1% of protium remained; PrOpionic acid-0,0-dg The methylmalonic acid—a-d-carboxylfigg was distilled at atmospheric pressure and then redistilled to give pure propionic acid-0,04g2. Propionamide-d,d-g2 To 55.00 g. (0.46 mole) of propionic acid-d,afd2 was added 54.8 g. (0.46 mole) of purified thionyl chloride (101). The mixture was refluxed for 1 hr. on a steam bath, cooled, and taken up into 800 ml. of dry ether. The ether solution was poured into a 2 liter 5-necked round-bottom flask equipped with a gas inlet tube, dry ice cold finger condenser, and a paddle stirrer. Anhydrous ammonia gas was introduced above the ether solution. On condensing the ammonia dripped into 68 the ether solution. The solid formed was filtered off and the ether and ammonia were removed by fractional distilla- tion. The remaining solid was purified by crystallization from ether. Yield: 25.9 g. (79%). m.p. 78-790. Propionitrile-d,dfg2 To 25.9 g. (0.545 mole) of propionamide-d,d-g2 was added 61.6 g. (0.518 mole) Of thionyl chloride. The mixture was heated on a steam bath for 2 hrs., taken up into 500 ml. of ether, washed with 50 ml. of 10% sodium carbonate solution saturated with sodium chloride, dried over anhydrous magnesium sulfate, and distilled. Yield: 14.24 g. (72.4%), b.p. 97o. 1-Propanol-2,21d2 To 11.40 g. (0.50 mole) of lithium aluminum hydride in 200 ml. of ether was added drOpwise 20.12 g. (0.26 mole) of propionic acid-a,dfig2 in 50 ml. of ether. After reflux- ing on a steam bath for 2 hrs., 55 g. of water was added and the solid was washed with ether. Upon fractional distilla- tion of the ether 15.25 g. (95.2%) of 1-propanol-2,2jd2 was obtained. Deamination of 1:propylammonium-1,1-d2 perchlorate (84) To 9.52 g. (0.06 mole) of 1-propylammonium—1,1fig2 perchlorate dissolved in 10 ml. of water and 7.15 g. (0.05 mole) of 70% perchloric acid was added dropwise with con- stant stirring over a 1 hr. period a solution of 8.80 g. 69 (0.127 mole) of sodium nitrite in 15 ml. of water. The reaction mixture was distilled into a receiver cooled in ice. When approximately 2/5 of the solution was distilled over, the distillation was stopped and the distillate was saturated with potassium fluoride and extracted with three 50 ml. portions of ether. The ether was dried over anhydrous magnesium sulfate and fractionally distilled. The yield of 1- and 2-propanol was 1.56 g. Deamination of 1-propylammonium-2,2:d2 perchlorate (84) The procedure was the same as that used in the deamina— tion of 1-propylammonium-1,1ag2 perchlorate. A 0.08 mole quantity of the amine salt was used. Yield: 0.86 g. of 1- and 2-propanol. Deamination of 2-propylammonium perchlorate (84) The procedure was the same as that used in the deamina- tion Of 1-propylammonium-1,1igg perchlorate. Twenty g. (0.126 mole) of the amine salt, 17.6 ml. of 55% perchloric acid, and 18.6 g. (0.27 mole) of sodium nitrite in 25 ml. of water yielded 5.2 g. of alcohol. Neopentyl-1,1fig2 ammonium perchlorate To 5.00 g. (0.072 mole) of lithium aluminum deuteride in 200 ml. of ether was added dropwise over a 1 hr. period with stirring, at 0°, 6.25 g. (0.075 mole) of Efbutyl cyanide in 50 ml. of ether. The reaction mixture was then Slowly warmed and refluxed for 5 hrs. The reaction mixture 70 was successively hydrolyzed with 5 m1. of water, 5 ml. of 20% aqueous sodium hydroxide, and 10 ml. of water. The ether layer was decanted from the solid material, the solid was repeatedly washed with ether, and the extracts were combined. To the ether was added 10.76 g. (0.075 mole) of 70% perchloric acid with subsequent vigorous shaking. The ether and water were removed under vacuum and the perchlorate salt was purified by precipitation from prheptyl alcohol with pfheptane (84). Yield: 15.77 g. (72.6%), m.p. 168-1690. Deamination of neopentyl-1,ifgg-ammonium perchlorate The procedure was similar to that used in the deamina- tion of 1-propylammonium-1,1fid2 perchlorate. The reaction mixture was extracted directly with ether and without the use of potassium fluoride. The reaction of 11.55 g. (0.062 mole) of the amine salt in 10 ml. of water and 4.4 ml. of 70% perchloric acid with 9.15 g. (0.155 mole) of sodium nitrite in 15 ml. of water yielded 2.90 g. (55.5%) of p-amyl alcohol. Neopentyl-1,1jg2 alcohol To 2.79 g. (0.067 mole) of lithium aluminum deuteride in 200 ml. of ether was added dropwise with stirring, at 00, 6.79 g. (0.067 mole) of trimethylacetic acid in 50 ml. of ether. The reaction mixture was refluxed for 5 hrs. and then hydrolyzed with 5% sulfuric acid. The ether layer was 71 dried with anhydrous magnesium sulfate and fractionally distilled. Yield: 5.28 g. (88.0%), m.p. 46-470. Neopentyl-1,1jg2 tosylate (67,102) To 6.27 g. (0.07 mole) of neopentyl-1,1fig2 alcohol in 25 ml. of pyridine was added 15.5 g. (0.07 mole) of tosyl chloride in 25 ml. of pyridine. The reaction was run at room temperature and allowed to stand for 90 hrs. After extraction with ether and 10% sulfuric acid, crystallization from p-pentane gave 14.96 g. (88.2%, m.p. 42-440) of the tosylate. Solvolysis of neopentyl-1,1figz tosylate (58) To a mixture of 100 ml. of water, 100 ml. of glacial acetic acid, and 7.7 g. of potassium acetate was added 14.96 g. (0.06 mole) of the tosylate. The reaction mixture was kept at 900 with stirring for 297 hrs. Upon neutrali- zation of the acid with 20% aqueous sodium hydroxide, ex- traction with 150 ml. of ether, and fractional distillation, 0.80 g. (14.5%) of Efamyl alcohol was obtained. .p—Butyllithium (105) In a 250 ml. glass-stoppered Erlenmeyer flask contain- ing 50 ml. of mineral Oil, 5.20 g. (0.750 mole) of lithium metal was heated to 2100 and shaken vigorously until the temperature was about 150°. The lithium sand and Oil were cooled to room temperature and 150 ml. of dry ether was added. The lithium was filtered off in a funnel containing 72 a glass wool plug. The lithium was washed with dry ether and added to 500 ml. 5-necked S 24/40 round-bottomed flask equipped with a nichrome wire stirrer with a ground-glass seal, a condenser containing a suspended thermometer, and a dropping funnel. To the top of the condenser were consecu— tively attached an anhydrous magnesium perchlorate trap, an aqueous saturated barium hydroxide trap, and a potassium hydroxide (pellets) trap. To the lithium in 200 ml. of dry ether was added dropwise with stirring 27.8 g. (0.50 mole) of Efbutyl chloride in 75 ml. of dry ether at -55 to —40°. The reaction mixture was dark grey in color. Trimethylacetic-i-l3C acid (105) To 27.25 g. (0.158 mole) of 56.5% enriched barium carbonate (Bio-Rad Laboratories) was added dropwise 71.8 g. (0.500 mole) of 70% perchloric acid. The resulting carbon dioxide was passed through two gas washing bottles contain- ing concentrated sulfuric acid and bubbled into the Efbutyl lithium-ether solution (0.75 mole), with the temperature being kept between -50 and -60°. After the addition of all the perchloric acid, the system was flushed with dry nitro— gen. The reaction mixture was then hydrolyzed with 10% hydrochloric acid at -500 and then let warm to room tempera- ture. The ether layer was extracted with 10% sodium carbonate and dried over anhydrous magnesium sulfate. Upon distillation of the ether solution, approximately 1 g. of a 50-50 mixture of trijpebutylcarbinol (13COH)-and difipfbutyl ketone (13C=O) 75 was Obtained. These were separated by VPC on a 10 ft. x i-in. Carbowax 20 M on 60/80 Chromasorb W column. Upon acidifica- tion of the sodium carbonate extract, extraction with ether, and fractional distillation, 12.81 g. (90.8%, b.p. 162—1640) of trimethylacetic-1—13C acid was obtained. Neopentyl-1-13C alcohol To 10.0 g. (0.25 mole) of lithium aluminum hydride in 200 ml. of ether was added drOpwise with stirring, at 00, 9.89 g. (0.10 mole) of trimethylacetic-1-13C acid in 50 ml. of ether. The reaction mixture was refluxed for 5 hrs. and hydrolyzed with 10% sulfuric acid. The product was vacuum distilled to give 7.84 g. (92.8%, m.p. 55-540) of alcohol. Neopentyl-1-13C tosylate (67,102) The procedure was the same as that used in the prepara- tion of neOpentyl-1,1fig2 tosylate. Five 9. (0.056 mole) of alcohol and 10.72 g. (0.056 mole) of tosyl chloride were used. Yield:: 11.59 g. (92.5%, m.p. 46-470). Solvolysis of neopentyl-1-13C tosylate (58) The procedure was the same as that used in the solvoly- sis of neopentyl-1,1fg2 tosylate. About 11.6 g. (0.048 mole) of the tosylate gave 0.4 g. of Eramyl alcohol. Trimethylacetamide-1-13C (104) To 5.00 g. (0.05 mole) of trimethylacetic—1-13C acid was added 8.45 g. (0.07 mole) of thionyl chloride. The 74 reaction mixture was refluxed for 5 hrs., cooled to 0°, and added dropwise to 200 ml. of concentrated ammonium hydroxide. Crystallization of the amide from 50-50 v/v petroleum ether— ethyl acetate gave 4.90 g. (99.0%) of the amide melting at 156-157°. Trimethylacetonitrile-l-l3C To 4.90 g. (0.048 mole) of trimethylacetamide-1-13C was added 8.60 g. (0.07 mole) of thionyl chloride (101). The reaction mixture was refluxed for 1 hr. and distilled. Yield: 1.09 g. (27.0%, I.R. 4.50 u, 4.60 u). Neopentyl-1-13C-ammonium perchlorate The procedure was the same as that used in the synthe- sis of neopentyl-1,15g2-ammonium perchlorate. The reaction of 5.80 g. (0.10 mole) of lithium aluminum hydride in 150 ml. of ether with 1.0 g. (0.01 mole) of trimethylacetonitrile-l- 13C in 50 ml. of dry ether, followed by the reaction of the resulting amine with 1.72 g. (0.01 mole) of 70% perchloric acid yielded 1.70 g. (75.6%, m.p. 168—1690) of the perchlorate. Deamination of neopentyl-1-l3C-ammonium perchlorate The procedure was the same as that used in the deamina- tion of neopentyl-1,1fig2-ammonium perchlorate. The reaction of 5.10 g (0.017 mole) of the perchlorate with 2.5 ml. of 55% perchloric acid and 2.45 g. (0.056 mole) of sodium nitrite in 10 ml. of water gave 0.6 g. of Eramyl alcohol. 75 Neopenpyl:1:i3c iodide (86) To 15.5 g. (0.05 mole) of triphenylphosphite was added 10.5 g. (0.074 mole) Of methyl iodide. The mixture was re- fluxed for 50 hrs., cooled, and washed with dry petroleum ether. To 12.1 g. (0.058 mole) of the methyl triphenylphos— phonium iodide was added 2.88 g. (0.027 mole) of neopentyl- 1—13C alcohol. The mixture was refluxed for 24 hrs. After extracting with 150 ml. of ether and washing with 100 ml. of 20% aqueous sodium hydroxide, the ether solution was dried and fractionally distilled to give 4.68 g. (88.5%) of the iodide. Solvolysis of neopentyl-1-13C iodide (60) To 20 ml. of water containing 2.75 g. (0.016 mole) of silver nitrate was added 2.68 g. (0.014 mole) of the iodide. The reaction mixture was stirred for 12 hrs., saturated with sodium chloride, and extracted with 150 ml. of ether. The ether extract was dried over anhydrous magnesium sulfate, filtered, and fractionally distilled. Yield: 0.79 g. (65.8%) of Efamyl alcohol. Neopentyl-1-13C chloride (86) To 54.00 g. (0.110 mole) of triphenylphosphite was added 15.00 g. (0.105 mole) of benzyl chloride. The mixture was heated at 1750 for 90 hrs. After cooling, the mixture was extracted with 500 ml. of dry ether. To 50.7 g. (0.07 mole) of the solid benzyltriphenylphosphonium iodide, remaining 76 after the ether extraction, was added 5.00 g. (0.056 mole) of neopentyl-1-13C alcohol. The mixture was heated at 600 for 60 hrs. and then distilled under reduced pressure (1 mm. of Hg) into a receiver cooled in liquid nitrogen. 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