Decarboxylation of 6‐nitrobenzisoxazole‐3‐carboxylate ion in cationic micelles: Effect of head group size

Abstract

AbstractThe rate of decarboxylation of 6‐nitrobenzisoxazole‐3‐carboxylate ion increases sharply with increasing head group size in a series of cetyltrialkylammonium bromides (C16H33NR3Br: R = Me, CTABr; R = Et, CTEABr; R = n – Pr, CTPABr; R = n – Bu, CTBABr) with rate enhancements of 102 (CTABr) and 2·8 × 103 (CTBABr). Micellized tetradecylquinuclidinium bromide and hexadecyl‐N‐methylmorpholinium bromide are slightly better catalysts than CTABr, as is 1,3‐bis(N‐cetyl‐N,N‐dimethylamino)propane dibromide, but p‐octyloxybenzyltrialkylammonium bromides (alkyl = Me, n – Bu) are less effective than the corresponding CTA+ surfactants. These differences in catalytic efficiency depend on the head group structure and the extent to which the cationic head groups become less accessible to water rather than the overall micellar structure.