Oxidation of organic sulfides by peroxyl radicals; search for an adduct intermediate

The reaction mechanism of dimethyl sulfide oxidation by peroxyl radicals (C Cl3OO. and CHCl2OO.) in aqueous/ alcohol solutions has been studied by mean s of pulse radiolysis with optical detection in order to gain evidence for the formation of an adduct intermediate, ROO-S-.(CH3)(2). In the range of 3 00-650 nm, the only absorbing product was the one-electron oxidized species [(CH3)(2)S . (.).S(CH3)(2)](+), and no indication of an additional absorpt ion attributable to an adduct precursor was found. Under the condition of o nly 50% conversion of CHCl2OO. into the sulfide radical cation, however, ad dition of a small amount of I- resulted in formation of (CHS3)(2)S . (.).I as the only product and at a yield equal to that of CHCl2OO. radicals. This result is explained by the reaction of iodide ions with a precursor of [(C H3)(2)S . (.).S(CH3)(2)](+) species, namely, the adduct CHCl2OO-S-.(CH3)(2) and is, thus, taken as conclusive, although indirect, evidence of the exis tence of this adduct intermediate.