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Kinetics and Mechanism of Oxidation of l-Histidine by Permanganate Ions in Sulfuric Acid Medium

Authors

  • A. FAWZY,

    Corresponding author
    1. Chemistry Department, Faculty of Applied Sciences, Umm Al-Qura University, Makkah Al-Mukarramah, Saudi Arabia Kingdom
    2. Chemistry Department, Faculty of Sciences, Assiut University, Assiut, Egypt
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  • S. S. ASHOUR,

    1. Chemistry Department, Faculty of Applied Sciences, Umm Al-Qura University, Makkah Al-Mukarramah, Saudi Arabia Kingdom
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  • M. A. MUSLEH

    1. Chemistry Department, Faculty of Applied Sciences, Umm Al-Qura University, Makkah Al-Mukarramah, Saudi Arabia Kingdom
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  • This article was published online on 28 April 2014. Errors were subsequently identified. This notice is included in the online and print versions to indicate that both have been corrected 15 May 2014.

ABSTRACT

The reaction kinetics for the oxidation of l-histidine by permanganate ions have been investigated spectrophotometrically in sulfuric acid medium at constant ionic strength and temperature. The order with respect to permanganate ions was found to be unity and second in acid concentration, whereas a fractional order is observed with respect to histidine. The reaction was observed to proceed through formation of a 1:1 intermediate complex between oxidant and substrate. The effect of the acid concentration suggests that the reaction is acid catalyzed. Increasing the ionic strength has no significant effect on the rate. The influence of temperature on the rate of reaction was studied. The presence of metal ion catalysts was found to accelerate the oxidation rate, and the order of effectiveness of the ions was Cu2+ > Ni2+ > Zn2+. The final oxidation products were identified as aldehyde (2-imidazole acetaldehyde), ammonium ion, manganese(II), and carbon dioxide. Based on the kinetic results, a plausible reaction mechanism is proposed. The activation parameters were determined and discussed with respect to a slow reaction step.

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