Thermodynamic, Kinetic and Mechanistic Investigations of Ruthenium(III) Catalyzed Methylparaben Oxidation by Diperiodatocuprate(III) in Aqueous Alkaline Medium

Abstract

The kinetics of ruthenium(III) catalyzed degradative oxidation of methylparaben by the copper complex, diperiodatocuprate(III) in alkaline medium is studied at 25ºC and at a ionic strength of 8.0 × 10⁻² mol dm⁻³. In the presence of catalyst ruthenium(III), the reaction between methylparaben and diperiodatocuprate(III) in aqueous alkaline medium exhibits 1:1 stoichiometry. The oxidation products were identified by UV-visible, GC-MS and IR spectroscopy. The reaction exhibited unit order in case of diperiodatocuprate(III) and ruthenium(III) concentrations, while less than unit order with respect to methylparaben and alkali concentrations. The added periodate retards the rate of reaction. The effect of added products, ionic strength and dielectric constant on the rate of the reaction were studied. The active species of diperiodatocuprate(III) and ruthenium(III) in alkaline media are [Cu(H₂IO₆)(H₃IO₆)]²⁻ and [Ru(H₂O)₅(OH)]²⁺ respectively. The activation parameters with respect to the rate determining step and the thermodynamic quantities with respect to the equilibrium steps are evaluated and discussed. The plausible mechanism in consistent with the experimental results is proposed and discussed in detail.

Keywords: Kinetics, oxidation, diperiodatocuprate(III), ruthenium(III), methylparaben