A Kinetic and Mechanistic Study on the Reduction of Dithizone by Stannous Chloride (acidic medium) in Micellar System

Kinetic studies on the reduction of dithizone by stannous chloride was carried out in acidic medium (HCl) at room temperature. The study was made in the presence of cationic surfactant, Cetyl Trimethyl ammonium Bromide (CTAB) and anionic surfactant, Sodium Dodecyl Sulphate (SDS). The reduction of dithizone in the presence of CTAB is much faster than in the absence of surfactant in acidic medium. As the concentration of acid increases the rate of the reaction also increases. No significant change was observed with SDS. The significant rate enhancement of these reactions in presence of CTAB micelles is due to the hydrophobic and electrostatic interactions between the substrate, reductant and micelles. These effects are discussed on the basis of interactions of the above compounds and micelles of different charge type. Mechanism of the reaction has been proposed consistent with the experimental findings. The binding constant between the substrate and CTAB micelles in HCl medium has been calculated by analyzing the data using pseudo phase model and found to be 757 M .