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Kinetic and Mechanistic Investigation on the Zirconium(IV)-Catalyzed Oxidation of L-Histidine by Hexachloroplatinate(IV) in Acid Medium

Research Authors
Ahmed Fawzy, Ishaq A. Zaafarany
Research Abstract

Kinetic investigation on the hexachloroplatinate(IV) (HCP) oxidation of L-histidine (His) catalyzed by zirconium(IV) has been performed in sulfuric acid medium at constant ionic strength and temperature. The reaction has been followed spectrophotometrically. A first order dependence on [HCP] and fractional-first order dependences with respect to [His], [acid] and [Zr(IV)] are obtained. Increasing ionic strength and dielectric constant decreases the oxidation rate. On the basis of the experimental results, a suitable mechanism has been proposed. The reaction is suggested to proceed via formation of zirconium(IV)-histidine intermediate complex, which reacts with the oxidant by an inner-sphere mechanism leading to decomposition of the complex in the rate-determining step to give rise to the oxidation products which are identified as the corresponding aldehyde (2-imidazole acetaldehyde), ammonium ion and carbon dioxide. The appropriate rate law is deduced and the activation parameters are evaluated and discussed.

Research File
Research Journal
Chemical Science Review and Letters
Research Member
Research Vol
4
Research Year
2015
Research Pages
608-618