An electron spin resonance study of the reactions of oxidising radicals with dialkyl sulphides. Radical cations derived from anodic oxidation of R2S, (R2N)2S, and (R2N)2SO
Abstract
Constant current electrochemical oxidation of R2S, (R2N)2S, and (R2N)2SO gives rise to radical cations which have been detected by e.s.r. spectroscopy. Dialkyl sulphides, except di-t-butyl sulphide which afforded the spectrum of But2S+˙, gave the dimer cations (R2SSR2)+˙. Bis(dialkylamino) sulphides or sulphoxides gave monomer cations in which a large fraction of the spin density is on nitrogen. The g factors of (R2SSR2)+˙ increase with the bulk of R, and the g factors of both (R2SSR2)+˙ and But2S+˙ are dependent on the temperature, the solvent, and the counteranion. The sulphide cation radicals have also been generated by photolysis of solutions containing R2S, ButOOBut, and CF3CO2H, and formation probably involves oxidation of the sulphide by ButȮH. The neutral radical ButO· and Me3SiO· react with dialkyl sulphides by abstraction of hydrogen from an α-C–H group or by competing addition to sulphur to form a sulphuranyl radical. The e.s.r. spectra of the adducts R2ṠOSiMe3 have been detected and these radicals appear to be non-planar at sulphur with the unpaired electron probably confined to an S–O σ* orbital.