Ester Cleavage Properties of Synthetic Hydroxybenzotriazoles in Cationic Monovalent and Gemini Surfactant Micelles

Bhattacharya, Santanu and Kumar, Praveen V (2005) Ester Cleavage Properties of Synthetic Hydroxybenzotriazoles in Cationic Monovalent and Gemini Surfactant Micelles. In: Langmuir, 21 (1). pp. 71-78.

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Abstract

Four 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 $pK_a$ 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.

Item Type:	Journal Article
Publication:	Langmuir
Publisher:	American Chemical Society
Additional Information:	Copyright for this article belongs to American Chemical Society.
Department/Centre:	Division of Chemical Sciences > Organic Chemistry
Date Deposited:	21 Feb 2005
Last Modified:	19 Jan 2012 09:31
URI:	http://eprints.iisc.ac.in/id/eprint/2798

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