Oxidation Studies with Peroxomonophosphoric Acid. III. A Kinetic and Mechanistic Study of Oxidation of Dialkyl Sulfides

Article abstract of DOI:10.1246/bcsj.53.2366

The kinetics of oxidation of dialkyl sulfides by peroxomonophosphate in aqueous medium at 308 K and μ= 0.4 mol dm^-3 follow the rate expressions (i) -d/dt= 1(H2PO5^1-)+k₂(HPO5^2-)> in the pH region 6.8-8.7 where k₁ and k₂ values are 336.5 and 0.95, 69.7 and 0.254, and 27.5 and 0.126 dm³ mol^-1 s^-1 for dimethyl, diethyl and dipropyl sulfides, respectively, (ii) -d/dt= k₂(HPO5^2-)* in the pH region 8.5-12.5, where the average k₂ values are 0.86, 0.247, and 0.128 dm³ mol^-1 s^-1 for dimethyl, diethyl, and dipropyl sulfides, respectively, and (iii) -d(peroxomonophosphate)/dt= 2(HPO5^2-)+k₃*(PO5^3-)> in the pH region 12.5-13.7, the k₂ and k₃ values being 0.947 and 0.107, and 0.233 and 0.018 dm³ mol^-1 s^-1 for dimethyl, and diethyl sulfides, respectively.The mechanism of the reaction is in line with a nucleophilic attack of the sulfide-sulfur on the peroxo oxygen, giving rise to S_N2-type transition states which undergo oxygen-oxygen bond fission to give the corresponding sulfoxide and phosphate.