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Ester Cleavage Properties of Synthetic Hydroxybenzotriazoles in Cationic Monovalent and Gemini Surfactant Micelles
journal contribution
posted on 2005-01-04, 00:00 authored by Santanu Bhattacharya, V. Praveen KumarFour new hydroxybenzotriazole derivatives have been synthesized. Two of them, N-tetradecyl-1-hydroxy-1H-benzo[d][1,2,3]triazole-6-carboxamide (2) and N-tetradecyl-1-hydroxy-1H-benzo[d][1,2,3]triazole-7-carboxamide (3), possess long alkyl chains, while the other two, 1-hydroxy-1H-benzo[d][1,2,3]triazole-6-carboxylic acid (4) and 1-hydroxy-1H-benzo[d][1,2,3]triazole-7-carboxylic acid (5), have carboxylate side
chains. These compounds along with their parent unsubstituted 1-hydroxybenzotriazole (HOBt), 1, have
been examined for the cleavage of p-nitrophenyl hexanoate (PNPH) and p-nitrophenyl diphenyl phosphate
(PNPDPP) in comicelles with monovalent cetyltrimethylammonium bromide (CTABr) and the corresponding
bis-cationic gemini surfactants 16-m-16, 2Br- of identical chain length at 25 °C and pH 8.2. The apparent
pKa values of the HOBt derivatives in the comicelles of CTABr or 16-4-16 gemini surfactant have been
determined from the rate versus pH profiles and were found to be comparable. Catalytic system 4/16-4-16
demonstrated over 2200- and 1650-fold rate enhancements in the hydrolysis of PNPDPP and PNPH,
respectively, for identical reactions carried out at pH 8.2 and 25 °C in buffered aqueous media. The second-order rate constants for such bimolecular reactions were determined employing pseudophase micellar
models. Experiments in which excess substrate was taken over HOBt derivatives demonstrated that the
catalysts “turned over”; hydrolysis of the putative acylated or phosphorylated HOBt intermediates was
rapid in either type of host micelles.
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benzosurfactantcomicelleEster Cleavage PropertiesPNPHhydroxybenzotriazolepseudophase micellar modelscarboxylate side chainsacidphosphorylated HOBt intermediatestetradecylPNPDPPhydroxypHnitrophenyl diphenyl phosphatetriazoleHOBt derivativeshydrolysismonovalent cetyltrimethylammonium bromideGemini Surfactant MicellesCTABr
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