KINETICS AND MECHANISM OF OXIDATION OF DIMETHYL SULFIDE WITH MOLECULAR-OXYGEN CATALYZED BY K[RUIII(EDTA-H)CL] COMPLEX IN WATER DIOXAN MEDIUM

Oxidation of dimethyl sulfide (Me2S) with molecular oxygen catalysed by [Ru(III)(EDTA)(H2O)]- 1a (EDTA = ethylenediaminetetraacetate anion) was studied spectrophotometrically in water-dioxan medium at constant pH 5.0 (acetic acid-acetate buffer) and ionic strength 0.2 M (KCl). The reaction proceeds through the formation of a [Ru(III)(EDTA)(Me2S)]- 2 intermediate which undergoes oxidation with molecular oxygen to give dimethyl sulfoxide (Me2SO) as the oxidation product. The rate of formation of 2 and its decomposition was followed spectrophotometrically by monitoring the reactions at 528 nm the characteristic peak of 2. The rate of formation of 2 was found to be first order in the concentrations of la and Me2S. The rate of decomposition of 2 is independent of the concentration of Me2S and is half-order with respect to oxygen concentration. Both the formation and decomposition reactions of 2 were studied at different temperatures, and the activation parameters DELTA-H(not-equal) and DELTA-S(not-equal) were determined. A suitable mechanism was proposed for the catalytic oxidation of dimethyl sulfide to dimethyl sulfoxide with molecular oxygen.