N-BROMONICOTINAMIDE OXIDATION OF ESSENTIAL AMINO ACIDS. A KINETIC STUDY

摘要

The kinetics of oxidation of essential α-amino acids, namely, lysine, histidine and arginine by N-bromonicotinamide(NBN) in aqueous acetic acid medium in the presence of hydrochloric acid was studied over the temperature range 308-328°C. It was studied in aqueous acetic acid medium at constant ionic strength. The kinetics was followed in acetic acid-water (1:1) solutions. The reaction was found to be first order with respect to substrate concentration. Inverse first order was observed with respect to concentration of oxidant and mineral acid. Added nicotinamide retarded the reaction. Mercuric acetate had no significant effect on the reaction rate. A decrease in the dielectric constant of the medium increases the rate. The amino acids were oxidised to the corresponding aldehydes, carbon dioxide and ammonia. The products obtained were isolated and identified. HOBr has been postulated as the reactive oxidising species in the reaction. The reaction rates were determined at 5 different temperatures and the thermodynamic parameters were evaluated.