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 HClO4. 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.