Kinetics of oxidation of pantothenic acid by choramine-T in perchloric acid and in alkaline medium catalyzed by OsO4:: A mechanistic approach

Kinetics of oxidation of pantothenic acid (PA) by sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) in the presence of HClO4 and NaOH (catalyzed by OsO4) has been investigated at 313 K. The stoichiometry and oxidation products are same in both media; however, their kinetic patterns were found to be different. In acid medium, the rate shows first-order dependence on [CAT](O), fractional-order dependence on [PA](o), and inverse fractional-order on [H+]. in alkaline medium, the rate shows first-order dependence each on [CAT](O) and [PA](O) and fractional-order dependence on each of [OH-] and [OsO4]. Effects of added p-toluenesulfonamide and halide ions, varying ionic strength, and dielectric constant of medium as well as solvent isotope on the rate of reaction have been investigated. Activation parameters were evaluated, and the reaction constants involved in the mechanisms have been computed. The proposed mechanisms and the derived rate laws are consistent with the observed kinetics. (c) 2005 Wiley Periodicals, Inc.