The reactivity and microscopic polarity studies in the sodium dodecyl sulfate based reversed micellar system

The catalytic effect of the sodium dodecyl sulfate-alcohol-water reversed micellar system on the basic hydrolysis of O-ethyl-O-p-nitrophenylethylphosphonate has been studied when varying the nature of oil phase and the component ratio. To test the micropolarity in the reaction site, the solvatochromic behavior of the 2,6-diphenyl-4-(2,4,6-triphenyl-1-pyridinium)phenoxide reagent has been examined in conditions analogous to those in the kinetic study. The values of the empirical parameter E-T (kcal/mol) have also been calculated. The E-T parameter and reactivity are found to depend on the nature and content of alcohol and on the surfactant and water concentration. The comparative analysis of kinetic data and the E-T values have shown that an increase in the polarity of the microenvironment of the reagents results in the decrease in their reactivity. A quantitative treatment of kinetic data in terms of the pseudophase model confirmed a considerable contribution of the microenvironmental factor to the above catalytic effect. (C) 2004 Elsevier B.V. All rights reserved.