Phase-Transfer Model for the Dynamics of “Micellar Autocatalysis”

The biphasic alkaline hydrolysis of ethyl caprylate (EC) exhibits highly nonlinear kinetics that has been attributed in the literature to “micellar autocatalysis” (Bachmann, P. A. et al. Nature 1992, 357, 57). New experimental results enable us to establish a macroscopic kinetic model quantitatively accounting for the dynamics of this reaction. According to the model, EC is carried from the organic to the aqueous phase by a transient micelle-EC complex (MEC). Curve fitting of the experimental kinetic data by inverse treatment shows that the formation of MEC is more favorable than that of the pure caprylate micelles (M) and occurs at a critical concentration that is smaller than the cmc associated with the formation of M. We demonstrate, in contrast to previous claims, that classical micellar catalysis is not involved in the overall reaction process, but the observed nonlinear kinetics is a consequence of the dynamics of the MEC-mediated phase-transfer reaction.