Kinetics and mechanism of oxidation of starch with sodium hypochlorite

Kinetics of heterogeneous oxidation of starch with hypochlorite were studied under varying conditions of temperature, pH, buffer components, buffer concentration, and concentration of substrate and oxidant. The kinetic data show that the reaction is first order with respect to hypochlorite. A plot of first-order rate constant for varying starch concentrations versus starch concentration is linear. The rate of oxidation of starch is highest at pH 7.0 and decreases with increasing acidity or alkalinity of the medium. In unbuffered system, pH of the medium decreases from 10 to 3.4 during the reaction. Based on observed trends of reaction rate, energy, and entropy of activation, a mechanism for hypochlorite oxidation of starch is proposed.