Intramolecular catalysis. Part 9.1 The hydrolysis of p-nitrophenyl acetate catalysed by imidazoles having proximate carboxylate groups
- 1 January 1997
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 2,p. 219-222
- https://doi.org/10.1039/a605649k
Abstract
The rate coefficients for the hydrolysis of p-nitrophenyl acetate catalysed by a series of imidazoles, 4,5-diphenylimidazoles, benzimidazoles and perimidines in 30 mol% aqueous dimethyl sulfoxide at 30.0 °C have been measured, as have the pKa values of the catalysts in the same medium. The effect of a 2-(2-carboxyphenyl) substituent in each system has been studied. The pKa values of the imidazolium and related ions show that the 2-carboxylate group increases their acidity by 1.03 to 1.32 pKa units. The same effect on the nucleophilicity of the corresponding imidazole and related compounds gives rise to rate increases of a factor of 1.4 to 3.2. These effects are related to the structure of the imidazoles, indicating the importance of the environment of carboxylate groups.Keywords
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