Asok K. Jana*1, G. Subashini1 and Papiya Jana2
1Department of Chemistry, Kanchi Mamunivar Centre for Post-Graduate Studies, Pondicherry-605008, India
2Department of Chemistry, Sri Manakula Vinayagar Engineering College, Pondicherry 605107, India
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, ks and rate constant in micellar phase, km 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