Kinetics and mechanism of the oxidation of dimethylsulfoxide (DMSO) and methanesulfinate (MSI-) by OH radicals in aequeous medium

Kinetics and product distribution of the reaction of dimethylsulfoxide (DMSO) and methanesulfinate (MSI-) with OH radicals and H2O2 in the aqueous phase are reported in this work. DMSO is found to be very stable in pure water or in solutions containing H2O2. On the other hand, it reacts very rapidly (k=4.5×109 M-1 s-1) with OH radicals. MSI- has been identified as the main intermediate product, while methanesulfonate (MS-) and sulfate were the final products due to the very fast reaction of MSI- with OH radicals (k=1.2×1010 M-1 s-1). MS- has been identified as the major end product (yield higher than 95%) of both DMSO and MSI-reactions by OH radicals in aqueous solutions. The potential implications of these reactions for the biogenic sulfur cycle in the atmosphere are presented and discussed.