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IJC-A Vol.47A(08) [August 2008] >


Title: Oxidation of L-cystine by 12-tungstocobaltate(III) in aqueous perchlorate medium: A kinetic approach
Authors: Satpathy, Prasanna Kumar
Dash, Gobind Chandra
Mohanty, Prakash
Issue Date: Aug-2008
Publisher: CSIR
IPC CodeInt. Cl.⁸ C07B33/00
Abstract: The oxidation reaction of L-cystine with 12-tungstocobaltate(III) (CoˡˡˡW₁₂O₄₀⁵⁻ or CoˡˡˡW⁻⁵) has been studied spectrophotometrically over the range 1.15 ≤ 10³[H₄L²⁺]T. ≤ 3.5; 2.0 ≤ pH ≤ 5.0; 25ºC ≤ t ≤ 40ºC and I = 0.3 mol dm⁻³ (NaClO₄). Both the conjugate bases of L-cystine participate in the electron transfer reaction. The rate of the reaction has been found to increase with the increase in pH and [L-cystine]T. The reaction shows first order dependence both on [CoˡˡˡW⁻⁵] and [L-cystine]T. The ΔH (kJ mol⁻¹) and ΔS (J K⁻¹ mol⁻¹) for k₁ and k₂ paths are 16.9±2.0, 16.1±0.5 and –205±6, –204±1.5, respectively. Negative activation entropy is indicative of ordered transition state for the reaction. The product of the reaction has been found to be the cystinesulphoxide.
Page(s): 1199-1203
ISSN: 0376-4710
Source:IJC-A Vol.47A(08) [August 2008]

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