Palladium(II)-catalyzed oxidation of tranexamic acid by bromamine-B in alkaline medium and uncatalyzed reaction in acid medium: A study of kinetic and mechanistic chemistry

Abstract

Tranexamic acid (TA) possess antifibrinolytic properties and finds extensive applications in pharmaceuticals. Its oxidation-kinetic study is of much significance in understanding the mechanistic profile of TA in biological systems. In this context, a systematic kinetic study of palladium(II) (Pd(II)) catalyzed oxidation of TA by sodium N-bromobenzenesulfonamide or bromamine-B (BAB) in alkaline medium and uncatalyzed reaction in perchloric acid medium at 303 K was investigated. In acid medium, the reaction exhibits a first-order dependence of rate on [BAB] o and less than unity order dependence on [TA] o. The reaction rate shows inverse less than unity order dependence with respect to [H +]. In alkaline medium, the reaction shows first-order dependence on both [BAB] o and [Pd(II)] and zero-order with respect to [TA] o. The order with respect to [OH −] is less than unity. Activation parameters have been evaluated. The oxidation reactions are nearly 10-fold faster in acid medium in comparison with alkaline medium. In alkaline medium, the Pd(II) catalyzed reactions are about 6-fold faster than the uncatalyzed reaction. Further, the catalytic constant ( K C ) has been calculated at different temperatures and activation parameters with respect to Pd(II) catalyst have also been evaluated. The conjugate acid C 6H 5SO 2NHBr and the anion C 6H 5SO 2N −Br of BAB have been postulated as the reactive oxidizing species in acid and alkaline media, respectively. The proposed mechanisms and derived rate laws are in agreement with the observed kinetics.