Electron spin resonance studies. Part 57. Alkane- and arene-sulphinate esters: an investigation of their photochemical decomposition and reactions with the t-butoxyl radical

E.s.r. evidence is described for three modes of photolytic decomposition of sulphinate esters [XS(O)OR]. For some alkyl arenesulphinates (X =p-tolyl, R = alkyl) the arenesulphinyl radical (XSO·) is detected, evidently as a result of S–O bond fission; for some alkyl alkanesulphinates, photolysis apparently cleaves the O–R bond and alkane-sulphonyl radicals (XSO2·;) are formed; for methyl phenylmethanesulphinate (X = PhCH2, R = Me) the detection of the benzyl radical and MeOSO· suggests that the C–S bond has been broken.It is suggested that the reaction between ButO·(from di-t-butyl peroxide) and sulphinates usually involves attack at sulphur to give an intermediate sulphuranyloxyl radical XṠ(O)(OR)OBut. Evidence that this can undergo dealkylation derives from the detection of the benzyl radical in the reaction of PhCH2S(O)OMe. On the other hand, the production of sulphonyl radicals (XSO2· X = alkyl, aryl) from this intermediate may involve dealkoxylation and further reaction of the resulting t-butyl sulphinate ester.Line-width variation in the e.s.r. spectrum of MeSO2· at low temperature is attributed to the occurrence of restricted rotation about the C–S bond in a radical of pyramidal type.