Kinetic study of the hydrolysis of substituted N-benzoylimidazoles and N-benzoyl-N'-methylimidazolium ions in light and heavy water. Hydrogen bridging without rate-determining proton transfer as a mechanism of general base catalyzed hydrolysis and a model for enzymic charge-relay
Rates and kinetic solvent isotope effects for the title substrates have been studied at 15 deg . Isotope effects kH2O/kD2O on the order of 2.5, essentially independent of substituent, were found for the uncatslyzed'' hydrolysis of both substrates, as well as benzoylimidazolium ions, and for the methylimidazole-catalyzed hydrolysis latter -kHO-of 1.2 to 1.4, larger for more electron-supplying substituents, as expected for simple ratedetermining nucleophilic attack on the carbonyl carbon atom. The lyoxide term for the benzoylimidazoles has isootope effects near 1.0. It is concluded that general base catalyzed hydrolysis, with water, methylimidazole, or lyoxide as general base as the case may require, is the problem mechanism for all terms studied (except the one case of simple nucleophilic attack), and that this mechanism consists of rate-determining nucleophilic attack by water with one proton partly transferred to the general base but not being transferred as part of the reaction coordinate motion.
- Research Organization:
- Univ. of Pennsylvania, Philadelphia
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-29-024008
- OSTI ID:
- 4310050
- Journal Information:
- Journal of the American Chemical Society, Vol. 96, Issue 5; Other Information: Orig. Receipt Date: 30-JUN-74; ISSN 0002-7863
- Publisher:
- American Chemical Society (ACS)
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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