Electron spin resonance studies of radicals formed during the thermolysis and photolysis of sulphoxides and thiolsulphonates

E.s.r. spectroscopy has been employed to characterize radical pathways in the thermal and photolytic decomposition of a variety of diaryl sulphoxides and aryl arenethiolsulphonates (ArSO2SAr). For the sulphoxides, S–C bond cleavage leads to the formation of the delocalized and relatively unreactive sulphinyl radicals (ArSO·); their subsequent reaction evidently involves disproportionation to sulphonyl (ArSO2·) and thiyl (ArS·) radicals. This pair of radicals is also formed directly in the homolysis of the thiolsulphonates, and the subsequent formation of sulphinyl radicals has been investigated. The results are analysed in terms of the products of the reactions and the efficacy of some of the parent substrates as antioxidants.