Effects of nonionic micelles on the rate of mononuclear heterocyclic rearrangement of (Z)-phenylhydrazones of 5-substituted 3-benzoyl-1,2,4-oxadiazoles

Nonionic Triton X-100 micelles solubilize the otherwise water-insoluble (Z) -phenylhydrazones of some 5-substituted 3-benzoyl-1,2,4-oxadiazoles to an e xtent suitable for studying the occurrence of a general-base-catalyzed rear rangement in the presence of borate buffers (pH 9.6). The kinetic data, obt ained at 40.0 degreesC over a wide range of surfactant concentrations, are found to conform to a reaction scheme which implies partitioning of the sub strates and the base between water and the micellar pseudophase. Evidence t hat both the rate of the rearrangement reactions and the binding of the sub strates to the micellar aggregates are primarily governed by the steric req uirements of the 5-substituent group is obtained. (C) 2001 Academic Press.