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Advances in Physical Chemistry
Volume 2012 (2012), Article ID 143734, 5 pages
http://dx.doi.org/10.1155/2012/143734
Research Article

Kinetics and Mechanism of Oxidation of L-Ascorbic Acid by Pt(IV)(aq) in Aqueous Hydrochloric Acid Medium

1PG Department of Chemistry, Utkal University, Odisha, Bhubaneswar 754004, India
2PG Department of Chemistry, Ravenshaw University, Odisha, Cuttack 753003, India

Received 30 June 2012; Accepted 20 September 2012

Academic Editor: Marc Koper

Copyright © 2012 Sadhana Senapati et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Reduction of [PtCl6]2− by L-ascorbic acid (H2ASc) in 0.1 M aqueous acid medium has been investigated spectrophotometrically under pseudo-first order condition at [PtCl6]2− = 0.005–0.007 mol dm−3, 0.05 ≤ [H2ASc]/mol dm−3 ≤ 0.3, 298 K ≤ ≤ 308 K, [H+] = 0.14 mol dm−3,  mol dm−3. The redox reaction follows the rate law: d[Pt(IV)]/dt = [H2ASc][Pt(IV)], where is the second-order rate constant and [H2ASc] is the total concentration of ascorbic acid. Electron transfer from [H2ASc] to Pt(IV) center leading to the release of two halide ions and formation of the reaction products, square planner Pt(II) halide complex, and dehydrated ascorbic acid is suggested. This redox reaction follows an outersphere mechanism as Pt(IV) complex is substituted inert. Activation parameters were calculated corresponding to rate of electron transfer reaction . Activation parameters favor the electron transfer reaction.