Physicochemical studies of water-in-oil nonionic microemulsion in presence of benzimidazole-based ionic liquid and probing of microenvironment using model C–C cross coupling (Heck) reaction

Abstract

The present report focuses on the evaluation of the interfacial composition and the thermodynamics of the transfer of 1-pentanol (Pn) from a continuous oil phase to the interface of w/o nonionic microemulsion [Tween-20/Pn/cyclohexane(Cy)/water] in the absence and the presence of an ionic liquid (IL) (1-butyl-3-propylbenzimidazolium bromide) under different physicochemical conditions [viz. variation in concentrations of IL (0.0 → 0.20 mol dm⁻³) and temperature (293 → 323 K] at a fixed molar ratio of water to surfactant (ω) by the Schulman's method of cosurfactant titration at the oil/water interface. The overall transfer process has been found to be spontaneous, exothermic and organized in the absence or the presence of IL, but shown to be influenced by [IL]. The microstructure and state of water organization inside a pool of these systems have been characterized by different experimental techniques, e.g., conductivity, DLS and FTIR in the absence or the presence of IL. In addition, a C–C cross coupling reaction (Heck reaction) has been employed to explore the properties of IL (additive) in the confined environment of the microemulsion vis-à-vis its interaction with the constituents of the interface. The reaction progress has been monitored using the above techniques. The reaction ended with the highest yield (75%) in the presence of 0.05 mol dm⁻³ of IL, wherein the microemulsion forms spontaneously with the highest stability.