Mechanism of oxidations by chloramine-T. Part I. Oxidation of α-hydroxy-acids

Kinetics of the osmium(VIII)-catalysed oxidation of glycollic, lactic, and mandelic acids have been investigated in alkaline media. First-order rate plots in chloramine-T were linear up to two half-lives. However, under pseudo-first-order conditions the rate constants showed a slight decrease with increase in chloramine-T concentration. The rate of reaction was independent of α-hydroxy-acid concentration and directly proportional to the osmium-(VIII) and the reciprocal of the hydroxide ion concentrations. The formation of a complex between N-chlorotoluene-p-sulphonamide and osmium(VIII) is rate-determining and is followed by the rapid transfer of a hydride ion from the substrate to this complex.