Mononuclear rearrangements of heterocycles in zwitterionic micelles of amine oxide surfactants

Rate constants for the mononuclear rearrangement(MRH) of Z-phenylhydrazones of some 5-substituted- 3-benzoyl-1,2,4oxadiazoles in water have been measured in the presence of zwitterionic micelles. The use of micellized N-tetradecyl-N,N-dimethylamineoxide(C14DMAO) as the reaction medium allowed to solubilize the otherwise water-insoluble oxadiazoles. Micellar rate effects were analyzed by using a simple pseudophase model and compared with those obtained in non-ionic micelles(TritonX-100). Evi- dence that both the rate of the rearrangement reaction and the binding of the substrates to the micelles are mainly governed by substrate hydrophobicity is obtained. The disagreement with the primarily sterically controlled MRH in TritonX100 micelles highlights large and intriguing differences between the two micellar environments.