Marija Bonifacic, Igor Stefanic
Ruder Boskovic Institute, Department of Physical Chemistry, Bijenicka c. 54, 10000 Zagreb, Croatia
The reaction mechanism of dimethyl sulfide oxidation by peroxyl radicals (CCl3OO· and CHCl2OO·) in aqueous/alcohol solutions has been studied by means 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 300-650 nm, the only absorbing product was the one-electron oxidized species [(CH3)2S\S(CH3)2]+, and no indication of an additional absorption attributable to an adduct precursor was found. Under the condition of only 50% conversion of CHCl2OO· into the sulfide radical cation, however, addition of a small amount of I- resulted in formation of (CH3)2S\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 [(CH3)2S\S(CH3)2]+ species, namely, the adduct CHCl2OO-·S(CH3)2 and is, thus, taken as conclusive, although indirect, evidence of the existence of this adduct intermediate.