Acid Hydrolysis of Bromazepam Catalyzed by Micelles, Reverse Micelles, and Microemulsions

Kinetics of the acid hydrolysis of bromazepam (Bz) has been investigated in micelles, reverse micelles, and microemulcions of cetyltrimethylammonium bromide (CTAB) by spectrophotometric method. The rate of the acid hydrolysis of Bz was found to be enhanced both below and above the critical micelle concentration (CMC) of CTAB in aqueous solution. The pseudo-first-order rate constant ( ) shows an initial decrease for both low and high H + concentrations. With further increase in [CTAB], at low [H + ], the attains an almost constant value, while, at high [H + ], the passes through a maximum and then decreases. The kinetic data for catalysis by micelles of CTAB was interpreted with the pseudophase ion exchange (PIE) model. In CTAB/cyclohexane/1-butanol/water microemulsions, as the water to surfactant ratio ( ) increases, the physicochemical properties and droplet sizes of microemulsions significantly change and distinct changes in reaction environment can be marked. The rate of the hydrolysis reaction exhibits excellent correlation with the physicochemical properties and droplet sizes of the microemulsions and reverse micelles of CTAB. At [H + ] = 0.001 M, in reverse micelles and microemulsions of CTAB, the of the acid hydrolysis of Bz decreases sharply followed by a slight increase with increasing

Dynamic Percolation and Swollen Behavior of Nanodroplets in 1‑Ethyl-3-methylimidazolium Trifluoromethanesulfonate/Triton X‑100/Cyclohexane Microemulsions

Microemulsions comprising an ionic liquid (IL), 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([emim]­[OTf]), as the polar component, Triton X-100 as a surfactant, and cyclohexane as the nonpolar medium were prepared and characterized. Conductivity and dynamic viscosity data were critically analyzed to confirm dynamic percolation among the droplets that are in continuous motion, aggregation, and fission. The transition from oil-continuous phase to bicontinuous phase was observed at the conductance and viscosity percolation thresholds and sharp changes in the values of conductivity and dynamic viscosity could be identified. Dynamic light scattering measurements revealed swelling of the droplets, which varied within the hydrodynamic diameter range of 10–100 nm. Diffusivity of the droplets suggested less Brownian movement with increased amount of the IL. Moreover, changes in the droplet sizes and diffusivity with increase in IL content supported dynamic percolation within the systems