Effects of surfactant and urea additions on the oxidation of phenylhydrazinium chloride by hexacyanoferrate(III)

The oxidation of phenylhydrazinium chloride (PhNHNH2) by hexacyanoferrate(III) ([Fe(CN)6]3−) has been studied in aqueous solutions. Typical saturation behavior was reached at [PhNHNH2]≥0.005 M in the absence and presence of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) micelles. The kinetic data have been used to obtain the complex formation constant, KIP and the electron transfer rate constant, ket. The obtained values (KIP and ket) were found to be decreased in the presence of AOT micelles. The observed rate constants (kobs) decrease with increase in (AOT) at 30 °C. The observed data have been treated with a pseudo-phase model of the micelle. The rate of reaction has also been studied at several urea concentrations in water and in the presence of AOT micelles at different temperatures. Activation parameters (ΔH* and ΔS*) were obtained from Eyring equation. These results have been explained taking into account the influence of structural changes occurring in water–urea and water–urea-AOT systems.