The oxidation of simple aliphatic sulphides [MeSMe, EtSEt, (CH,),S] by hydroxyl radicals occurs via a complex reaction mechanism. The first step is addition of the OH* to sulphur to form R2SOH radicals. At low sulphide concentrations ( < ~O -* M ) R,SOH rapidly eliminates H 2 0 to form a RSR(-H)* radical which may be described by the mesomeric forms -CH-S-and -CH=S-.This radical is ultimately also formed at higher sulphide concentrations but via a different pathway. R2SOH increasingly reacts with another R2S molecule to form a short lived (R,S),OH* radical complex which dissociates to (R,S),+ and OH-. The (R,S),+ complex ion seems to be relatively stable and decays essentially via equilibration to the molecular cation R2S+. This ion in its reaction with the solvent, OHions, and through a bimolecular process with another R2S+ cation is effectively deprotonated to form the RSR( -H). radical. The reaction route a t high concentration includes the formation of transient species with oxidizing properties; Fe(CN)64is rapidly oxidized by (R,S),+ [and possibly (R,S),OH*].The RSR(-H).radical partially disproportionates to negative and long lived (>I ms) positive ions. The stable oxidation product, sulphoxide, has been identified.

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