Abstract

MECHANISTIC INVESTIGATION OF OXIDATION OF VITAMIN B6 BY DIPERIODATOARGENTATE(III) IN AQUEOUS ALKALINE MEDIUM

Deepa G. Patil and Sharanappa T. Nandibewoor*

Abstract

The kinetics of oxidation of vitamin B6 (Pyridoxine Hydrochloride) by diperiodatoargentate(III) (DPA) in aqueous alkaline medium at a constant ionic strength of 0.50 mol dm-3 was studied spectrophotometrically. The main oxidation product was identified as aldehyde (pyridoxinal). The stoichiometry was [Vit B6]: [DPA] = 1:1. The reaction was first order with respect to [DPA] whereas the order with respect to vitamin B6 and alkali concentrations changes from first order to zero order as the vitamin B6 and alkali concentrations are increased. Addition of periodate had no effect on the rate of the reaction. Effect of added products, ionic strength and dielectric constant of the reaction medium has been investigated. Based on experimental results, a mechanism involving complex formation between DPA species and vitamin B6 was proposed. The reaction constants involved in the mechanism were evaluated. The activation parameters with respect to the slow step of the mechanism were determined and discussed.

Keywords: DPA, Vitamin B6, oxidation, uncatalysed, mechanism and kinetics.