Kinetic Studies of Micelle-Assisted Redox reactions in aqueous Media

Asok K. Jana*¹, G. Subashini¹ and Papiya Jana^2
1Department of Chemistry, Kanchi Mamunivar Centre for Post-Graduate Studies, Pondicherry-605008, India
²Department of Chemistry, Sri Manakula Vinayagar Engineering College, Pondicherry   605107, India

Abstract
The rate constant of three redox reactions: i) Fe³⁺ — H₂O₂, ii) S₂O₈ ^2-—I^– and iii) BrO₃^–—I^– were determined in aqueous media in the absence and presence of surfactants: cationic, CTAB; anionic, SLS and nonionic, Triton X -100 at 30⁰C and 44.3⁰C, respectively. The rate as well as rate constant of Fe³⁺ -H₂O₂   system increases with increase in concentration of ionic (CTAB and SLS) and nonionic (TX -100) surfactants at room temperature. The trend of enhancement of rate constant of Fe³⁺ -H₂O₂   system follows the order: CTAB> TX -100> SLS at room temperature but at high temperature, the order: CTAB> SLS> TX -100. For BrO₃^–—I^–and S₂O₈ ^2-—I^– systems, the rate constant‘s enhancement follow the following order at both temperatures: CTAB> TX -100> SLS. Thermodynamic properties as well as activation energies of activated state of these kinetics have been determined. With the help of Bruice’s mathematical model and Menger and Portnoy’s equation, the association constant, k_s and rate constant in micellar phase, k_m for the redox reactions in different surfactants micellar pseudo phase at 30⁰C and 44.3⁰C have been calculated.
Keywords: Redox reaction, Association constant, Micellar phase, Gouy -Chapman layer, binding ability