Ru(III)-Catalyzed Oxidative Cleavage of Ritodrine Hydrochloride: A Kinetic and Mechanistic Study

Abstract

A systematic kinetic and mechanistic study of the oxidation of ritodrine hydrochloride (RTH) with chloramine-T (CAT) in both HClO₄ and NaOH media has been carried out at 303 K. In acid medium, the reaction rate is very sluggish to be measured kinetically. Ruthenium (III) chloride ([Ru(III)]) was found to be an efficient catalyst. The reaction rate exhibits a first-order dependence on [CAT]₀ in both media. It shows a fractional-order on [RTH]₀ in alkaline medium whilst zero-order dependence in presence of HClO₄. The order with respect to [NaOH] and [HClO₄] is negative-fractional. The order with respect to [Ru(III)] is fractional. Dielectric effect is negative. Activation parameters have been evaluated. Oxidation products have been identified by LC-MS analysis. Further, it was found that these oxidation reactions are about five-times faster in alkaline medium in comparison to acid medium. It was also observed that Ru(III)was an efficient catalyst for the oxidation of RTH by CAT in acid medium. Nearly a four-fold acceleration in the rate relative to an uncatalyzed reaction is observed. The observed results have been explained by plausible mechanisms and the related rate laws.

Keywords: Ritodrine hydrochloride, Chloramine-T, Oxidation-kinetics, Ru(III) catalysis, Mechanism