Kinetics and mechanism of oxidation of sodium pyruvate by dihydroxydiperiodatonickelate(IV) in alkaline medium

Abstract

The kinetics of oxidation of sodium pyruvate (SP) by dihydroxydiperiodatonickelate(IV) (DPN) was studied by spectrophotometry between 288.2 K and 303.2 K in alkaline medium. The reaction rate showed first order dependence in DPN and SP. It was found that the pseudo-first order ([SP]0 >> [ Ni(IV)]0) rate constant, k obs, increased with increase in concentration of OH− and SP, but decreased when the concentration of IO 4 − increased. There was a negative salt effect and no free radical was detected. In view of this, the dihydroxyperiodatonickelate(IV) species is assumed to be the oxidizing specie. A plausible mechanism involving a two-electron transfer is proposed and the rate equations derived from the mechanism can explain all the experimental results satisfactorily. The activation parameters, as well as the rate constants of the rate-determining step have been calculated.