Mechanistic studies on the oxidation of some organic sulphides with quinolinium fluorochromate in nonaqueous medium

The oxidation kinetics of diphenyl, dialkyl and methyl phenyl sulphides has been investigated under pseudo-first-order conditions with quinolinium fluorochromate (QFC), a newly developed Cr(VI) reagent in acetonitrile medium. p-Toluene sulphonic acid (TsOH) is used for catalyzing the reaction. Initial-rate methods are used for determining the orders with respect to reactants in dialkyl sulphides. The oxidation is first-order with respect to [QFC] and second-order dependence is observed on [TsOH]. [Sulphide] has no effect on the reaction:rate. Diphenyl sulphide (DPS) oxidation follows the rate law, nu = kappa(2)K(1)[S][Ox][TsOH]. Acrylonitrile retards the rate of oxidation significantly in diphenyl sulphides indicating the involvement of free radical cation sulphur intermediate in the rate-limiting step. The Michaelis-Menten dependence each on [sulphide] and [TsOH] can be well explained by a two-pathway mechanism in methyl phenyl sulphide oxidation. The derived rate law, nu = kappa(1)[Ox][TsOH] + kappa(3)[Ox][S] is consistent with experimental observations.