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题名: The Catalytic Effect of Water in Basic Hydrolysis of Methyl Acetate: A Theoretical Study
作者: Haffner, F.;Hu, Ching-Han;Brinck, T.;Norin, T.
贡献者: 化學系
关键词: Ab initio;Ester hydrolysis;Solvation;Assistance;Ancillary water
日期: 1999-02
上传时间: 2012-05-03T06:16:31Z
出版者: Elsevier
摘要: Base catalyzed hydrolysis of methylacetate has been investigated at the ab initio MP2/6-31+G*//HF/6-31+G* level of theory. In the gas phase the BAC2-mechanism is favoured over the SN2-mechanism by 22kJmol-1 in the computed free energy of activation. Two water molecules were added to the tetrahedral intermediate and to the third transition state of the BAC2-mechanism to simulate specific solvation of the reacting species. One of the water molecules was found to take part in a water-assisted six-membered cyclic transition state. The polarized continuum solvent model (PCM) was applied to all the optimized geometries to simulate the aqueous bulk medium. The computed free energy of activation of the water-assisted second transition state is 14kJmol-1 lower than that of the corresponding non-assisted transition state. The BAC2-mechanism in aqueous solution is favoured over the SN2-mechanism by 56kJmol-1 in free energy of activation. The computed free energies of activation of the BAC2-mechanism in aqueous solution are in good agreement with experimental data.
關聯: Journal of Molecular Structure: THEOCHEM, 459(1-3): 85-93
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