Catalyzed Oxidation Kinetics of Some Drug Molecules A Mechanistic Investigation

Abstract

Redox chemistry of pharmaceutically and biologically important substances like Pregabalin, Taurine, Diphenhydramine HCl, Prilocaine HCl and Rizatriptan benzoate with N-metallo-N-haloarylsulphonamides such as Chloramine-T, Chloramine-B, Bromamine-T and Bromamine-B in the view point of their kinetics and mechanism have been examined under several experimental circumstances. Mechanistic study on the oxidation-kinetics of Pregabalin by acidic Chloramine-T with and without Ru(III) catalyst at 303 K have been examined. With the similar experimental set ups, the rate laws are, rate =kc[CAT]o[PG]xo[H+]-y[Ru(III)]z for catalyzed reaction and rate = ku[CAT]o [PG]xo [H+]-y for uncatalyzed reaction, where x, y lt 1 and z = 1. Kinetics of oxidation of Taurine by Bromamine-T in acidic medium using Ru(III) catalyst and in basic medium using Os(VIII) catalyst has been investigated at 313 K. The rate indicates unit order dependency on both [Ru(III)] and [BAT]o, negative fractional order on [H+] and independency on [TAU]o in acid medium. But, in basic medium, the observed rate suggests unit order dependency on each [BAT]o and [Os(VIII)], inverse less than unity order on [OH-] and fractional order on [TAU]o. Oxidation of diphenhydramine hydrochloride by basic Chloramine-B in presence of Ru(III)/Pt(IV) catalyst has been examined at 313 K. Positive dielectric effect has been detected in both the catalysis. The solvent isotope effect, k/(H2O)/k/(D2O), for Ru(III) and Pt(IV) reactions was observed to be 0.80 and 0.82 respectively. Kinetics and oxidative behavior of Prilocaine hydrochloride-Chloamine-B redox scheme in acidic medium without catalyst and in basic medium using Os(VIII) catalyst has been described at 308 K. It was discovered that OsO4 catalyzed reaction is nearly four times quicker than uncatalyzed reaction in basic medium. In both HClO4 and NaOH media, the activation parameters, decomposition constants, rate laws and reaction mechanisms have been suggested.