Kinetics and mechanism of Ru(III) catalyzed and uncatalyzed oxidation of atenolol by chloramine-T in perchloric acid medium

The kinetics and mechanism of chloramine-T (CAT)-oxidation of atenolol (ATN) in aqueous perchloric acid medium have been studied at 26 +/- 0.1 degrees C in the presence and absence of Ru(III) catalyst. Under identical experimental conditions, the reaction shows a first-order dependence on [CAT](0), a zero-under dependence on [ATN](0) and an inverse fractional-order dependence on [II] for both the Ru(III) catalyzed and uncatalyzed reactions. The order with respect to Ru(III) is unity. Variation of ionic strength and addition of p-toluenesulfonamide or chloride ion have no effect on the rate. Decrease in dielectric constant of the reaction medium decreases the rate constant in both cases. Activation parameters have been computed. The stoichiometry of the reaction is found to be 1:4 and the main oxidation products are identified as 4-acetamidobenzencoxyacetie acid and isopropyl amine. Based on the kinetic data, the conjugate acid, CH3C6H4SO2NHCl, is assumed to be the reactive oxidizing species in both cases. The Ru(III) catalyzed reactions are 2-3 times faster than the uncatalyzed reactions. Mechanisms consistent with the observed rate laws have been proposed.