Solubilization processes in autocatalytic biphasic reactions

The kinetics of solubilization of ethyl hexanoate into an aqueous phase was investigated in the presence of various additives (NaCl, ethanol, and sodi um hexanoate). The salting-out effect of NaCl and the solvent effect observ ed in the presence of ethanol were quantified. Solubilization by sodium hex anoate shows a dramatic enhancement when the critical micellar concentratio n is exceeded. This effect was interpreted by the formation of mixed oil/su rfactant aggregates. The kinetic rate constants of solubilization of ethyl hexanoate into the water phase were determined in the presence of sodium he xanoate using a model including salting-in, salting-out, and aggregation ef fects. When NaCl was replaced by NaOH, ethyl hexanoate was hydrolyzed to so dium hexanoate and ethanol. The kinetics of this reaction was recorded in t he same geometrical setup as for previous solubilization experiments. The s olubilization kinetic model was able to describe the hydrolysis reaction by just adding a rapid bulk hydrolysis step. The model quite accurately predi cts the autocatalytic effect of sodium hexanoate formation and the overall reaction time. This result clearly shows the crucial role of solubilization processes on this biphasic hydrolysis reaction.