Stoichiometry, Kinetics and Mechanism of Oxidation of L-Cysteine by Hexacyanoferrate (III) in Acidic Media

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Journal Title, Volume, Page: 
An-Najah University Journal for Research - Natural Sciences - Volume 10, Issue 1
Year of Publication: 
1996
Authors: 
Waheed J. Jondi
Department of Chemistry, Faculty of Science, An-Najah National University, Nablus, Palestine
Current Affiliation: 
Department of Chemistry, Faculty of Science, An-Najah National University, Nablus, Palestine
Mohammad M. Al-Subu
Department of Chemistry, Faculty of Science, An-Najah National University, Nablus, Palestine
Hani M. Abed
Rajab Abu El-Hallow
Preferred Abstract (Original): 

The Stoichiometry, kinetics, and mechanism of oxidation of L-cysteine by hexacyanoferrate (III) in acidic media at constant ionic strength have been studied spectrophotometrically. A1:1 L-cysteine:hexacyanoferrate (III) has been established with 1..-cysteine as the only product. The reaction is zero order in hexacyanoferrate (III), first order in L-cysteine and inverse first in hydrogen ion concentration. The activation parameters were evaluated in the temperature range 15-40°C (Ea.# = 28.2 kJ/mol.∆S# = -192.4 J/mol. deg). The oxidation was inhibited in the presence of added hexacyanoferrate (II). The effects of other added salts and composition of the solvent have been rationalized. Two mechanisms are offered to explain the kinetic data.

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