Non-ionic micellar inhibition on the rate of oxidation of l-histidine by alkaline hexacyanoferrate(III)

Abstract

The effect of non-ionic surfactants, viz., triton X-100, tween-80 and brij-35 on the rate of oxidation of l-histidine by hexacyanoferrate(III) in alkaline medium has been studied spectrophotometrically in the temperature range 35-55ºC. The rate of oxidation is strongly inhibited in presence of non-ionic micelle. The reaction follows a complex kinetics showing a first order dependence of rate with respect to both, alkali and l-histidine. During a particular kinetic run, a second-order dependence of rate with respect to hexacyanoferrate(III) is observed while an increase in initial [hexacyanoferrate(III)] or an addition of hexacyanoferrate(II) in the reaction mixture results in a decrease in the observed rate constant. A suitable mechanism has been proposed and the kinetic data accounted for by the association/distribution of the substrate in micellar and aqueous pseudo-phase. The binding parameters have also been evaluated.