Kinetics and mechanism of oxidation of carbohydrazide and thiocarbo-hydrazide by N-bromoacetamide

Abstract

Kinetics of oxidation of carbobydrazide (ch) by N-bromoacetamide (NBA) in aqueous perchloric acid medium and thiocarbohydrazide (tch) in the free state and in its metal complex by NBA both in the presence and absence of added bromide ion have been investigated in aqueous perchloric acid medium. Oxidation of carbohydrazide showed first order kinetics in [NBA], nearly first order in [ch] and inverse fractional order in [H+]. The rate slightly decreased with increase in ionic strength of the medium. Addition of either the reduced product of the oxidant or bromide had no significant effect on the rate of CH oxidation. Oxidation of thiocarbohydrazide in the free and metal-bound states both in the presence and absence of added bromide showed first order kinetics in [NBA] and fractional order in both [tch] and [H+]. But the fractional order in [H+] for the oxidation of tch in the presence of Br¯ was almost twice that in its absence. The rate increased with increase in [Br¯] with a fractional order of about 0–3. Variation in ionic strength of the medium had very negligible effects. Addition of acetamide, the reduced product of the oxidant, had no effect on the rate. Michaelis-Menten type mechanisms have been considered to explain the observed results. Activation parameters have been computed for all the oxidations by measuring rates at different temperatures. Detailed mechanisms of oxidations have also been suggested.