PROOF OF STRUCTURE OF SOME CONTROVERSIAL SULFONYL CHLORIDES by GEORGE BAKER McKEOWN H A THESIS Submitted in partial fulfillment of the requirements for the degree of Master of Science in Chemistry in the School of Chemistry in the Graduate School of the University of Alabama UNIVERSITY, ALABAMA 1960 I ACKNOWLEDGMENT I wish to express my great indebtedness to Dr. R. B. Scott, Jr. for his supervision and numerous suggestions during the course of this work. G. B. M. CONTENTS Page INTRODUCTION • • • • • • • • • • • • • • • • • • • 1 THE PHOTOCHEMICAL CHLOROSULFANYLATION OF ALKANES ••••••••••••• . 3 TERTIARY SULFONYL CHLORIDES •• . 9 DECOMPOSITION OF SULFONYL CHLORIDES • • 13 CONCERNING A CLAIM AND A COUNTER-CLAIM TO PREP.A~ING TERTIARY SULFONYL CHLORIDES PHOTOCHEMICALLY • • • • • • • • • 15 EXPERIMENTAL • • • • • • • • • • • • • • • • • • 17 Preparation of 4-Chloro-2-methyl-l-butanesulfonyl Chloride from 4-Chloro-2-Methylbutane. • • • • . 17 Preparation of 4-Hydroxy-2-methyl-l-butanesulfonic Acid Sultone. • • • . • • • • • • • • • • . • . • • • 18 Conversion of 4-Chloro-2-methyl-l-butanesulfonyl Chloride to 2-Methyl -1-butanethiol • . .. • • . • • • 19 Preparation of 2-Methyl-1-butanethiol from 2-Methyl- 1-butanol. • • • • • • • • • • . • • • • . • • • . • 21 Preparation of 4-Chloro-2-methyl-1-pentanesulfonyl Chloride • • . • • • • • . • • • • • • • • • • • • • • 23 Preparation of 4-Hydroxy-2-methyl-l-pentanesulfonic Acid Sultone . • • • • • • • • • • • • • • • • • • • 25 Conversion of 4-Chloro-2-methyl-1-pentanesulfonyl Chloride to 2-Methyl-1-pentanethiol • • • • • • • 2 6 Preparation of 2-Methyl-1-pentanethiol from 2- Methyl-1-pentanol . • • • • • . • • • • . • • 26 CONTENTS Page SUMMARY. 28 APPENDIX. 29 BIBLIOGRAPHY ..................... 34 INTRODUCTION A comprehensive investigation of reaction mechanisms of sulfonyl compounds was initiated in this Laboratory in 1949. At that time an insight into these reaction mechanisms was sought by determining the steric requirements of several branched chain sulfonyl chlorides so that they could be compared with analogously branched primary alkyl halides in order to test the assumption that the sulfonyl group acts as a pseudo-methylene group. In the course of the investigation the study has been broadened to include other types of sulfonyl compounds; namely, polyfunctional sulfonyl chlorides, sulfonic acid esters, and sultones. It has been claimed that photochemical chlorosulfonylations of isopentyl chloride and 4-methyl-2-pentyl chloride produce the corresponding chloro tertiary sulfonyl chlorides1 but evidence 1H. Helberger, G. Manecke, and H. Fischer, Ann., 562, 23 (1949). 1 2 1 2 developed in this Laboratory and elsewhere has almost conclu - sively proved that the sulfonyl chlorides are primary ones. The most convincing proof would be to convert the sulfonyl chlorides into substances of known structure. It was the purpose of this in­ vestigation to so prove the structures of these sulfonyl chlorides. It was decided to accomplish this proof by isolation of the sulfonyl chlorides (showing absence of isomeric products), conversion of these to the sultones (structures of which have been proved), and also reduction of the sulfonyl chlorides to the oorresponding un­ substituted mercaptans, with unequivocal synthesE:S of these mercaptans. As it is customary to establish identity of a liquid product with a solid derivative, it was decided to prepare such deri­ vatives of each sulfonyl chloride and mercaptan. 1 M. K. Frye, M. S. Thesis, 1951, University of Alabama., University, Alabama, and M. S. Heller, PhD Dissertation, 1955, University of Alabama, University, Alabama. 2 F. A singer and F. Ebeneder, Ber., 75, 344 (1942), and F. Asinger, G. Geiseler., and M. Hoppe, Ber., 91., 2130 (1953). THE PHOTOCHEMICAL CHLOROSULFONYLA TION OF ALKANES The conversion of alkanes to the corresponding alkanesulfonyl chlorides by the photochemical reaction of sulfur dioxide and chlo­ 1 rine with paraffin hydrocarbons (the Reed reaction ) is represented by the over-all equation: hv R-H + S02 + Cl2 Due to the unshared pair of valence electrons about the sulfur atom in sulfur dioxide, this compound may enter into the chain reaction which occurs during photochemical chlorination of hydrocarbons. Thus, with the conjoint action of sulfur dioxide and chlorine gases on saturated hydrocarbons in the liquid phase under strong illumina­ tion with short wave length visible or ultraviolet light sulfonyl chlo­ rides are obtained. The products, in addition to sulfonyl chlorides, usually include some chloroalkanes and polysulfonated material, 2 higher temperatures favoring chlorination. The reaction mechanism has been thoroughly studied and seems to indicate the following 1 C. F. Reed, U. S. Patent, 2,046,090 (June 13, 1936); Ref. cit., C. ~-, 30, 5593 (1936). 2 C. Walling, "Free Radicc3:ls in Solution" (John Wiley and Sons, Inc., New York, 1957), p. 394. 3 4 t 1;2;3,4 s eps: Cl hv 2c1· 2 + ... R-H + Cl· ... R· + HCl R" + S02 =- RSO2 · R· + Cl-Cl ._,, RCl + Cl· RS02· + Cl -Cl --t- RS02 Cl + Cl· 0 The quantum yield (3000-5000 A) is about 2000. The usual proce- dure for carrying out the reaction is to pass a mixture of chlorine and an excess of sulfur dioxide into an irradiated liquid phase of the hydrocarbon, with or without a suitable diluent such as carbon 0 tetrachloride, at about 10-30 . In this study the diluent was omitted. The reason for this was that neither Asinger nor Helberger mentioned a solvent. As one phase of the problem was to attempt to duplicate their yields, none was used. When a straight chain hydrocarbon is subjected to the above­ mentioned Reed reaction, the only sulfonyl chlorides obtained are 1F. Povenz, ~ Elektrochem., 56, 746 (1952). 2 J. Stauff, ibid., 49, 550 (1942). If 3P. Herold, Reichsamt Wirscmftsausbau;, Pruf - Nr. 102, (PB 52004), 69-74 (1940), C. A., 41, 6527 (1947). 4H. Helberger, Angew ~ Chem., 55, 172 (1942). 5 primary and secondary ones. 1 If the hydrocarbon contains tertiary hydrogen atoms there might be the theoretical possiblity of forming tertiary sulfonyl chlorides, for the tertiary hydrogen atom is the most susceptible and the primary least to analogous chlorinations. However, the tertiary sulfonyl chloride is very unstable for two rea­ sons; (1) the inductive effective of the side-chain weakens both the carbon-sulfur and the sulfur-chlorine bond, and (2) the backstrain (rrB"-strain) makes the compound less stable. Asinger2 claims to have prepared t-isobutanesulfonyl chloride by reacting the sodium salt of the corresponding sulfonic acid with phosphorus pentachloride. Unfortunately, a detailed description of experimental conditions was omitted in the publication. The product obtained is reported to be a stable liquid boiling at 80° /15 mm, which readily reacts "normally" with cyclohexyla:tnine to give a solid deriv­ ative melting at 61. 5°. Frye, 3 in this Laboratory and Hunt., 4 with duPont, were unsuccessful in duplicating A singer's work. However, Frye did prepare t-isobutanesulfonyl chloride by reacting t­ butylmagnesium chloride with sulfuryl chloride. This sulfonyl 1 F. A singer, W. Schmidt, and F. Ebeneder, ibid. , 75., 34 (1942). 2 F. Asinger and F. Ebeneder, ibid., 75, 344 (1942). 4See Appendix. 6 chloride melts at 89-91 ° as would be expected from its symmetrical structure. A solid derivative of the sulfonyl chloride could not be prepared in this Laboratory., indicating great steric hindrance to such a reaction. The t-isobutanesulfonyl chloride prepared by Frye rapidly de­ composes into t-butyl chloride and sulfur dioxide by first order kinetics. It has a half-life of 240, 34, and 6 hours at 25°., 35°, and 0 50 , respectively. 1 This is in accord with the belief that the simple tertiary sufonyl chlorides should be relatively unstable ("B"-strain). From this and other investigations conducted recently in this Laboratory it is believed that the compound prepared by Asinger is not a sulfony1 chloride. Photochemical chlorosulfonylation is applicable to all saturated alkanes above methane in the liquid phase; however, only a few of these give individual sulfonyl chlorides that can readily be isolated. Low molecular weight paraffins such as propane and butane yield mix­ tures of primary and secondary products which are easily 2 ., 3, 4, 5, 6 separat e d . Some branched chain paraffins such as 1Frye, op. cit. 2F. Asinger, W. Schmidt, and F. Ebeneder, loc. cit. 3 F. Asinger, F. Ebeneder, and E. Bock, ibid., 75, 42 (1942). 4F. Asinger and F. Ebeneder, ibid., 75, 344 (1942). 5H. Helberger, G. Manecke, and H. Fisher, loc. cit. 6A. P. Terent1 ov and A. r: Gershenovich, Zhur. Obshchei Khim., 23, 204 (1953). 7 isobutane1, 2, 3-dimethylbutane and neopentane3 give only one mono­ substituted products. This is also true of alicyclic alkanes such as cyclopentane4 and cyclohexane. 5 When long chain hydrocarbons are used a mixture of products is necessarily produced and separation of isomers is usually very difficult and impracticable. Chloro­ sulfonylation of such hydrocarbons takes place in a largely sta­ tistical manner6 as in the case of chlorination. When polysulfony­ lation occurs, the substituted positions are at least three carbon atoms apart. According to Lockwood7 when 10 to 20 per cent of the usual alkane is chlorosulfonylated, about 90 per cent of the sulfonation product is mono- and 10 per cent disulfonyl chlorides. At 50 per cent conversion, approximately 70 per cent is monosulfonyl chlorides, while with 70 per cent conversion about equal amounts of mono- and disulfonyl chlorides