Unraveling the Catalytic Dynamics of Mixed Micellar Assemblies: A Molecular Approach to Green Organic Oxidative Transformation Reaction

The formation of mixed micelles represents a promising strategy to enhance organic reactions in aqueous media, offering a sustainable approach to reaction optimization. This study investigates the catalytic oxidation of cyclohexanol by chromium(VI) under acidic conditions at 27 °C with reaction kinetics monitored using UV-vis spectroscopy. Three readily available surfactants, cationic cetylpyridinium chloride (CPC), non-ionic Brij-35 (polyoxyethylene (23) lauryl ether), and anionic sodium dodecyl sulfate (SDS), were utilized to construct two mixed micellar systems: cationic/non-ionic (CPC: Brij-35) and anionic/non-ionic (SDS: Brij-35). Both mixed micellar systems exhibited significant catalytic activity, with the CPC: Brij-35 system, at an equimolar ratio, enhancing the reaction rate by an impressive 13.97-fold, compared to a 9.87-fold increase observed for the SDS: Brij-35 system. The superior catalytic efficiency of the CPC: Brij-35 assembly is attributed to enhanced micellization, improved solubilization of cyclohexanol, and strong electrostatic interactions between the positively charged CPC and the slightly negatively charged Brij-35, as evidenced by zeta-potential measurements. The kinetic behavior of the reaction was meticulously analyzed via UV-vis spectroscopy, while the micellization phenomena were corroborated through dynamic light scattering, zeta potential analysis, scanning electron microscopy, and ¹H NMR spectroscopy. Additionally, the critical micelle concentrations (CMC) of the individual surfactants and their mixed systems were determined by using tensiometric measurements, providing a deeper understanding of the micellization process. The study reveals a plausible reaction mechanism emphasizing the critical role of the reaction zone within mixed micellar assemblies. These findings establish mixed micelles as powerful catalytic platforms, advancing green chemistry through an enhanced reaction efficiency and sustainable processes in aqueous media.