Decarboxylation of 6-Nitrobenzisoxazole-3-carboxylate Catalyzed by Ammonium Bilayer Membranes. A Comparison of the Catalytic Behavior of Micelles, Bilayer Membranes, and Other Aqueous Aggregates

Article abstract of DOI:10.1021/ja00547a009

Decarboxylation of 6-nitrobenzisoxazole-3-carboxylate was studied at 5-50 deg C in water in the presence of CTAB micelles, dialkylammonium (2CnN⁺2C1) bilayer membranes, and trioctylmethylammonium (TMAC) aggregates.These aqueous aggregates possess totally different morphologies with each other, but their general rate acceleration effects increased simply with increasing local hydrophobicities: CTAB < 2CnN⁺2C1 < TMAC.In contrast with the other systems, the rate enhancement by the dialkylammonium membrane was influenced by its hydrophobicity and fluidity.The crystal-to-liquid crystal phase transition determines the membrane fluidity.The Arrhenius plots for the membrane catalysis of 2CnN⁺2C1 (n = 12, 14, 16, 18) invariably showed inflections at or near the respective phase transition temperature (T_c).The activation energy data suggest that the membrane catalyst is governed mainly by the hydrophobicity and fluidity (or rather rigidity) at temperatures above and below T_c, respectively.