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 6 H 5 SO 2 NHBr and the anion C 6 H 5 SO 2 N − 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.

Oxidation of Tetracaine Hydrochloride by Chloramine-B in Acid Medium: Kinetic Modeling

“…CAB is analogous to CAT and exhibits similar equilibria in aqueous acidic and basic solutions [5,8,10,11]. In general, CAB undergoes a two-electron change in its reactions forming the reduction products, benzenesulfonamide (BSA; PhSO 2 NH 2 ) and NaCl.…”

Oxidative Cleavage of β-Lactam Ring of Cephalosporins with Chloramine-T in Alkaline Medium: A Kinetic, Mechanistic, and Reactivity Study

“…In the light of the above information and in continuation with our ongoing research on the oxidation kinetics and mechanism of important organic substrates [13][14][15], we report here the results obtained on the oxidation kinetics of three cephalosporin drugs, namely, cephalexin (CEX), cefadroxil (CFL), and cephradine (CPD) with CAT in alkaline medium in order to elucidate the mechanism of these redox systems and also to assess their relative rates. The studies were extended to deduce the appropriate kinetic rate law and also to establish the isokinetic relationship through the computed thermodynamic parameters.…”

“…where and are the reacting ions, and are the charges on the respective species, and are the rate constants in the presence and in the absence of the added electrolyte, respectively. Equation (14) shows that a plot of log versus 1/2 would be linear yielding a slope 1.02 and an intercept log . As the slope of the line depends on charges of the reacting ions, three special cases may arise: (i) if and have the same charges, will be positive and the rate constant increases with √ ; (ii) if and have opposite signs, will be negative and the rate constant decreases with √ ; and (iii) if either or is uncharged, is equal to zero and is independent of the ionic strength of the solution.…”

PdCl2 Catalyzed and Uncatalyzed N-Oxidation of Naratriptan with Alkaline Chloramine-T: Delineation of Reaction Mechanisms and Kinetic Modelings

“…The mechanisms of catalysis to some extent is complicated by the formation of different intermediate complexes, free radicals and different oxidation states [16,17]. Palladium (II) chloride (Pd(II)) has been used as a catalyst in the oxidation of several substrates in alkaline medium and some of them have been proved to be suitable for kinetic analysis [11,[18][19][20][21][22]. This background instigated us to carry out the detailed study on the kinetics and mechanism of NTT-CAT redox system in alkaline medium with and without Pd(II) catalyst.…”