Kinetic Study of Cysteine Oxidation by Potassium Hexacyanoferrate(III) in the Presence of Sodium Dioctylsulfosuccinate

The kinetic oxidation of cysteine (Cyst) by 0.001 M hexacyanoferrate(III) (Fe(CN)6 3−) in 0.06 M HCl at 25°C in aqueous and/or in and 0.005 M sodium dioctylsulfosuccinate (AOT) has been studied using optical absorption at 420 nm. The present data show that the reaction is first‐order with respect to [Cyst]T and Fe(CN)6 3−. Also, k obs is constant within the 0.05–0.10 M HCl range and decreases with increasing concentration of AOT up to 0.003 M, and then increases above 0.005 M AOT. The rate of the reaction in the presence of micelles can be explained using a pseudo‐phase model of the kinetics. Association constants of Cyst and Fe (CN)6 3− with AOT micelles are reported. The activation parameters ΔH # and ΔS # have also been obtained. The variation of the reaction rate with the nature of the salt is discussed.