KINETICS AND MECHANISM STUDIES OF OXIDATION OF Α-AMINO ACIDS BY N-BROMOSUCCINIMIDE

Kinetics and mechanism studies of oxidation of some α-amino acids (Proline, Arginine, Alanine) (AA) by N-Bromosuccinimide (NBS) by using conductivity method was carried out. The kinetic study showed that the reaction was first order with respect to NBS and AA. The effect of addition of HClO4 to the reaction was negative on the rate of reaction. The reaction was carried out at different temperatures in which G , S , were calculated. The rate of reaction of AA was as follows: Proline > Arginine > Alanine Key word: Kinetics , α-amino acids , N-Bromosuccinimide. Introduction NBS is considered as one of the oxidants that are used widely in oxidizing organic compounds (1-5) . It is also considered as important oxidant in oxidizing many coordination complexes (6-10) as well as oxidant in oxidizing biochemical compounds 11-12) . NBS is also used as initiator of polymerization in some reactions (13) . The literature presented Many reports about oxidation of AA (14) , but the kinetics of AA oxidation by NBS has not been reported. Experimental 1.Material: NBS supplied by Fluka of 98% purity, Succinimide and Arginine supplied by Riedel-de Hean of 98% and 96% purity respectively, Proline and Alanine supplied by Aldrich of 98% purity and double distillated water had been used. 2.Method: Three different concentrations of NBS were prepared in dark bottles to avoid the photolysis of NBS. All kinetic measurements were recorded by using digital conductivity meter wTw-540 (0.000S02.000mS±5%). The reaction was followed up through conductivity variation at time intervals. The conductivity of the solution was increasing with time due to hydrogen ion generation as reaction product. All experiments were carried out at constant volume of final solution (50ml). The reaction was carried out by adding materials of certain concentrations in to the reaction cell. The conductivity was recorded directly after mixing the materials quickly then the conductivity was recorded in times intervals. Results and Discussion 1Kinetic measurements: The study showed that conductivity increased with time due to generation H + as reaction product, therefore: t Represents unreacted concentration of NBS o Represents initial concentration of NBS where : : the conductivity after completion. t : the conductivity at time (t). o : the conductivity before starting the reaction. The kinetic study showed that the reaction was first order by using integral equations of reaction orders. Since the concentration of AA was several times more than the concentration of NBS, the reaction has been pseudo first order as follows: t o t In ( ) In ( ) k (1) Equation (1) reveals the first order expression using the conductivity symbols. Where: k = constant of reaction rate t = time