Free-radical-induced oxidative degradation of antibacterial drug, methylparaben by permanganate in alkaline medium: A kinetic and mechanistic approach

The kinetics of oxidation of an antibacterial drug, methylparaben by permanganate in alkaline medium at a constant ionic strength of 0.80 mol dm⁻³ was studied spectrophotometrically at 25°C. The stoichiometric ratio between permanganate and methylparaben was found to be 2:1 in alkaline medium. The main products were identified by NMR, IR, and GC–MS spectral studies. The reaction showed first-order kinetics in permanganate, fractional order in methylparaben, and OH⁻ concentrations under the experimental conditions. Ionic strength and dielectric constant did not affect the rate of reaction. The added products did not have any significant effect on the rate of reaction. Based on the rate experimental results, a suitable mechanism is proposed. Investigations at different temperatures allowed the determination of the activation parameters with respect to the slow step of the proposed mechanism. The reaction constants involved in the mechanism were evaluated. The results of this study provide fundamental mechanistic parameters and degradation efficiencies of drug by advanced oxidation processes.