Kinetics and mechanism of oxidation of carbohydrazide by chloramine-T and bromamine-T in aqueous perchloric acid medium

Abstract

Kinetics of oxidation of carbohydrazide by chloramine-T (CAT) and bromamine-T (BAT) have been studied in aqueous medium over a wide acid range, and are found to be [H+] dependent. At low [H+] (0-0005-0-0075 mol dm−3), oxidation by both CAT and BAT shows first-order kinetics in [oxidant], fractional order in [substrate] and inverse fractional order in [H+]. At [HClO4]>0-005 mol dm−3, the rate dependence in [H+] is zero and fractional order for CAT and BAT oxidations respectively and the kinetics in [oxidant] and [substrate] are the same as before. Two pathways as well as Michaelis-Menten type mechanisms have been discussed to explain the observed kinetics and other effects. The rate controlling steps have been identified and the coefficients of these steps and the corresponding activation parameters are calculated. The rate constants are also predicted from the rate laws as [substrate] and [H+] are varied. The predicted values are in reasonable agreement with the experimental rate constants.