International Journal of Modern Science and Technology
International Journal of Modern Science and Technology, 1(2), 2016, Pages 42-46.
Oxidative deamination and decorboxylation of leucine by 1-chlorobenzimidazole in acid medium-A kinetic approach
Department of Chemistry, Arasu Engineering College, Kumbakonam – 612 501. Tamil Nadu, India.
The oxidation of leucine (amino acid) by 1-chlorobenzimidazole (CBI) has been studied in 80% (v/v) acetic acid – water medium. The reactions were followed potentiometrically up to 70% completion, by following the potentials of the reaction mixture containing varying concentrations of [CBI]/[BI] couple (BI=benzimidazole) at regular time intervals using a platinum-saturated calomel electrode assembly. The pseudo first order rate constants, k1, were evaluated from the linear plots (r>0.999) of log (Et - Eα) Vs time. The reaction exhibits first order dependence each in [CBI] and [leucine] and inverse fractional order in [H+] ions. Decrease in dielectric constant of the solvent medium decreases the rate of reaction suggesting dipole–dipole type of reaction. The rate of reaction is not influenced by the addition of electrolyte like sodium perchlorate. The reaction rate was retarded by added benzimidazole, one of the reaction products. Polymerization was not observed when acrylonitrile is added to the reaction mixture. The kinetic runs were carried out at four different temperatures and thermodynamic parameters have been evaluated. Product analysis showed the formation of carboxylic acid, ammonia and carbon-dioxide. Carboxylic acid formation was confirmed by TLC, ammonia by Nessler’s reagent test and carbon-dioxide by lime water test. HOCl has been postulated as the most probable oxidizing species. A plausible mechanism in accordance with observed kinetic data has been proposed.
Keywords: Kinetics; Deamination; Decarboxylation; 1-Chlorobenzimidazole; Leucine.
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