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Effect of Surfactant on the Oxidation of M-Nitrophenol in Aqueous Acetic Acid Medium by Chloramine-T : A Kinetic Study

Geetha Sarasan

Oxidation of m-Nitrophenol by Chloramine-T has been investigated both in the presence and absence of the surfactant, Cetyl pyridinium bromide (CPBr). The reaction could be studied only at a moderate concentration of acid (acetic acid). Kinetic investigation revealed that the order of the reaction with respect to Chloramine-T is one in the absence of Cetyl pyridinium bromide (CPBr). But in the presence of surfactant, the values of first order rate constant increases with increasing concentrations of Chloramine-T. It is observed that the rate has almost ten times acceleration in the presence of cetyl pyridinium bromide due to the catalysis by micelle. The order with respect to substrate (m-nitrophenol) is found to be zero in the absence of the surfactant and fractional in the presence of the surfactant. The plot of log k versus 1/T for various values of temperature is a straight line, which proved the validity of Arrhenius equation. Activation parameters like ∆E* , ∆H* , ∆S* , ∆G* , are evaluated and a plausible mechanism is proposed.