Oxidation of metronidazole with sodium N-bromo- P-toluenesulfonamide in acid and alkaline media: A kinetic and mechanistic study

A kinetic study of oxidation of metronidazole (Met) with sodium N-bromo-p-toluenesulfonamide or bromamine-T (BAT) has been carried out in HClO 4 (30°C) and NaOH (40°C) media. The experimental rate laws obtained are -d[BAT]/dt = k[BAT][Met] x [H +] y in acid medium and -d[BAT]/dt = k[BAT][Met] x [OH -] y/[PTS] z in alkaline medium, where x, y, and z are less than unity and PTS is p-toluenesulfonamide. The reaction was subjected to changes in (a) ionic strength, (b) concentration of added reduction product PTS, (c) concentration of added neutral salts, (d) dielectric permittivity, and (e) solvent isotope effect. In both media, the stoichiometry of the reaction was found to be 1:1, and the oxidation product of metronidazole was identified as its aldehyde. The reaction was studied at different temperatures, and the activation parameters have been evaluated. The reaction constants involved in the proposed schemes were deduced. The reaction was found to be faster in acid medium in comparison with alkaline medium, which is attributed to the involvement of different oxidizing species. Mechanisms proposed and the rate laws derived are consistent with the observed kinetics. © 2005 Wiley Periodicals, Inc