RUTHENIUM (III) - CATALYZED OXIDATWE CLEAVAGE OF PHENYLPROPANOLAMINE HYDROCHLORIDE WITH SODIUM N-CHOROBEZENESULFONAMIDE IN ACID MEDIUM: A KINETIC AND MECHANISTIC STUDY

Abstract

Phenylpropanolamine hydrochloride (2-amino-1-phenylpropanol hydrochloride) is a sympathomimetric drug used for nasal congestion associated with the common cold, allergies, high fever, or other respiratory illness. The kinetics of oxidation of phenylpropanolamine hydrochloride (PPA) with sodium Nchlorobenzenesulfonamide or chloramine-B (CAB) catalyzed by Ru (III) in hydrochloric acid medium has been studied at 308 K. The oxidation reaction follows the rate law, - d [CAB]/dt = k [CAB][H+]x [PPA]y [Ru(III)]z, where x, y and z are less than unity. Addition of chloride ions, perchlorate ions and the reduction product of CAB, benzenesulfonamide (BSA), have no significant effect on the rate. Decrease of dielectric permittivity of the medium by increasing the CH 3 CN content increased the rate. The reaction was studied at different temperatures and the activation parameters have been computed from the Arrhenius plot. The stoichiometery of the reaction was found to be 1:1 and the main oxidation products of PPA were found to be benzaldehyde and acetaldehyde. The rate constant decreases in D 2 O medium and the normal isotope effect, k’ (H 2 O) / k’ (D 2 O) is 2.39. Proton inventory studies have been made in H 2 O-D 2 O mixtures. Formation and decomposition constant of CAB-PPA complexes in the reaction scheme have been evaluated. The conjugate acid C 6 H 5 SO 2 NHCl has been assumed to be the reactive species. The observed results have been explained by plausible mechanisms and relative rate law has been deduced.