Impact of Micelle Media on the Kinetics of Oxidation of l-Lysine (An Essential Amino Acid) by N-Bromophthalimide

Abstract

The effect of cationic surfactant cetyltrimethylammonium bromide (CTAB) on the oxidation of L-lysine by N-bromophthalimide (NBP) has been studied at 308 K. The reaction exhibits first order dependence on NBP and L-lysine and negative and fractional order dependence on HClO 4 . The effects of KCl, KBr, phthalimide, mercuric acetate, and dielectric constant of the medium have also been studied and summarized. CTAB strongly catalyzes the reaction and typical k obs and CTAB profile was observed, that is, with a progressive increase in CTAB, the reaction rate increased and after achieving a peak k obs decreased at higher concentrations of CTAB. The results are treated quantitatively in terms of 'Menger-Portnoy' and 'Piszkiewicz' models. The various activation parameters in presence and absence of CTAB have been also evaluated. A suitable mechanism consistent with the experimental findings has been proposed. The rate constant in micellar phase k M , cooperativity index (n) and binding constant have been computed.