Oxidation of dimethylsulphoxide by sodium m-bromobenzene- sulphonamide: A kinetic and mechanistic study

The kinetics of oxidation of dimethylsulphoxide (DMSO) by sodium N-bromobenzenesulphonamide or bromamine-B (BAB) has been studied in HClO₄, HCl and NaOH media, at 35°C, with OsO₄ as a catalyst in the latter medium. In acid medium, the rate shows a first order dependence on [BAB] and second order in [H⁺], but Is Independent of substrate concentration. Alkali retards the reaction (Inverse first order) and the rate is independent of oxidant concentration, but shows fractional order in [DMSO] and depends on (0sO4]². The solvent isotope effect was studied by using D₂O. Activation parameters have also been determined. Mechanisms proposed and the derived rate laws are consistent with the observed kinetics.