Kinetics and Mechanism of the Selective Oxidation of Benzoic and Isonicotinic Acid Hydrazides to their Corresponding Acids by Thallium (III) in Aqueous 1, 4-Dioxane Medium

Kinetics of the oxidation of benzoic and isonicotinic acid hydrazides has been studied by Thallium (III) in a mixture of perchloric and hydrochloric acid media at a constant ionic strength in 1, 4-dioxane-water medium, iodometrically. The reaction showed pseudo-first order. The reaction was found to fractional with [Hydrazide] and unity with [oxidant]. The reaction failed to induce the polymerisation of added acrylonitrile and this rules out the involvement of any radical intermediate in the reaction. The increase in [H+] and [Cl-] decreases the rate of the reaction. The increase in ionic strength does not affect the rate of reaction. The effect of temperature was studied at four different temperatures ranging from 150C to 300C. The order of reactivity among the studied hydrazides is isonicotinic acid hydrazide greater than Benzoic acid hydrazide. The Michealis - Menten plots of 1/kobs versus 1/ [Hydrazide] were linear with an intercept in support of the complex formation. Thermodynamic parameters were determined and a suitable mechanism is proposed in accordance with the obtained results.