MICELLAR EFFECTS UPON OXIDATION OF ORGANIC SULFIDES BY ANIONIC OXIDANTS

Peroxymonosulfate ion (HSO5-) rapidly oxidizes 2-chloroethyl phnyl sulfide (1). Dilute micelle-forming cationic surfactants slightly speed the reaction but the reaction rate decreases sharply with increasing surfactant concentration. Rate-surfactant concentration profiles in solutions of cetyltrimethylammonium hydrogensulfate can be treated quantitatively by estimating concentrations of 1 and HSO5- at the micellar surface with allowance for competition between HSO5- and HSO4-. The second-order rate constant in the micellar pseudo-phase is lower that in water by a factor of ca 400. Similar rate-surfactant concentration profiles were observed for the oxidation of di-n-propyl sulfide by periodate ion in solutions of cetyltrimethylammonium bromide, chloride and mesylate, and second-order rate constants in the micellar pseudo-phases are lower than in water by factors of ca 400. These oxidations are slowed by a decrease in the water content of aqueous acetonitrile and solvent, and micellar rate effects are consistent with transition states in which positive charge builds up on sulfur.