Kinetic studies on ph dependent oxidase vs. oxygenase mechanism for Ru(III)-EDTA catalyzed oxidation of allyl alcohol by molecular oxygen in aqueous acidic medium

Abstract

The kinetics of the oxidation of allyl alcohol by molecular oxygen catalyzed by Ru(III)-EDTA complex is investigated in the pH range 1.0-3.0 at 35°C (μ=0.1 M) in aqueous medium. In the pH range studied, the reaction is first order with respect to catalyst and substrate concentrations. An inverse first-order dependence on H⁺ concentration is observed below pH 2.0, while the rate is independent of [H⁺] above pH 2.0. The rate of reaction is independent of O₂ concentration at pH 1.5 and first order with respect to O₂ concentration at pH 2.5. Mechanisms for the oxidation of allyl alcohol catalyzed by Ru(III)-EDTA have been proposed in the pH ranges 1.0-2.0 and 2.0-3.0, wherein the reactions are shown to proceed through oxidase and oxygenase routes, respectively. The rate laws for these routes are derived and the corresponding rate constants reported.