Oxidation of L-Valine by Manganese(III) in Pyrophosphate Medium: Kinetics and Mechanism

Kinetics of oxidation of L-valine (Val) by manganese(III) pyrophosphate has been studied as a function of pH (0.94-1.90) at 313 K. The reaction shows a first-order dependence of rate each on [Mn(III)] and [Val], a fractional-order on [H+], and an inverse fractional-order each on [Na4P2O7] and [Mn(II)]. Effects on the rate of anions, such as [F-], [Cl-] and [ClO4-], and the dielectric constant of the solvent medium have been studied. Solvent isotope studies have been performed in D 2O medium. Activation parameters have been determined from Arrhenius and Eyring plots. A mechanism consistent with the observed kinetics is proposed and discussed.