Synthesis ofsome benzothiazole derivatives and kinetic studies of their oxidation using Chloramine-T in acid medium

The kinetics of oxidation of 2-phenyl-benzothiazole (BzlH), 2-(4-methoxyphenyl) benzothiazole (OMeBzlH), 2-(4-nitrophenyl)-benzothiazole (NO2BzlH) by chloramine-T; (CAT) in presence of HClO4 has been investigated at 296 K. Under similar experimental conditions, the oxidation reactions follow identical kinetics for all the three benzothiazoles with first order dependence each on [CAT]0 and [substrate]0 and inverse fractional order dependence on [H+]. Solvent composition shows negative effect indicating the involvement of negative ion-dipolar molecule in the rate determining step. Variation of ionic strength of the medium and addition of halide ions had no effect on the reaction rate. Addition of p-toluenesulphonamide (PTS), the reduction product also has no effect on the rate of reaction. The reactions were studied at different temperatures and the composite activation parameters have been computed. Relative reactivity of oxidation of these follow the order: OMeBzlH>BzlH> NO2BzlH. This trend may be attributed to inductive effects. The observed results have been explained by a plausible mechanism and the related rate law has been deduced.