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

1980; Oxford University Press; Volume: 53; Issue: 8 Linguagem: Inglês

10.1246/bcsj.53.2366

1348-0634

G. P. Panigrahi, Radhasyam Panda,

Chemistry and Chemical Engineering

Abstract 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[peroxomonophosphate]/dt={k1[H2PO5−]+k2[HPO52−]}[sulfide] 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[peroxomonophosphate]/dt=k2[HPO52−]·[sulfide] 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={k2[HPO52−]+k3·[PO53−]}[sulfide] 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 SN 2-type transition states which undergo oxygen-oxygen bond fission to give the corresponding sulfoxide and phosphate.