Effect of micellar aggregates on the kinetics of oxidation of α-aminoacids by chloramine-T in perchloric acid medium

The kinetics of oxidation of some alpha-aminoacids viz. alanine, phenylalanine and valine by chloramine-T in HClO4 medium have been investigated in absence and in presence of three types of surfactants, viz. an anionic (sodium lauryl sulphate), a cationic (cetyltrimethylammonium bromide) and a non-ionic (polyoxyethylene (23) lauryl ether, commonly known as Brij 35) surfactant. In absence of surfactant, the rate of oxidation may be represented as, d[chloramine-T]/dt = k[chloramine-T][aminoacid]/1 + K[H+] where k and K are the constants. The presence of a small amount of any surfactant well below its critical micelle concentration strongly enhanced the rate of reaction suggesting a premicellar aggregation. The kinetic data have been analysed in terms of earlier reported models for micellar catalysis. The binding constants between the reactants and the surfactant evaluated from the two models proposed by Piszkiewicz and Raghvan and Srinivasan are in good agreement. (c) 2005 Elsevier B.V All rights reserved.