Hydration and Hydrolysis of alpha-Oxo Carboxylic Acid Derivatives and Conjugate Addition to alpha,beta-Unsaturated Carbonyl Compounds: A Density Functional Study.
Hydration of the keto group as well as hydrolysis (ester and amide) of alpha-oxo carboxylic acid derivatives has been studied by density functional theory (B3LYP/6-31G and B3LYP/6-311G). Both uncatalyzed as well as water-assisted processes have been considered. Solvent effects were approximated by the self-consistent isodensity surface polarized continuum (SCIPCM) model. For hydrolysis reactions a concerted as well as a stepwise mechanism was calculated. In the latter one, addition of the nucleophile to a tetrahedral intermediate was found to be rate determining. In uncatalyzed processes both concerted and stepwise mechanisms are calculated to have comparable activation energies and free enthalpies. In catalyzed reactions the stepwise mechanism is predicted to be considerably more favorable. Hydration of the alpha-oxo group should be much more feasible than either ester or amide hydrolysis.
Janoschek
Rudolf
R
Institut für Theoretische Chemie, Karl-Franzens Universität Graz, Strassoldogasse 10, A-8010 Graz, Austria, and Institut für Organische Chemie, Karl-Franzens Universität Graz, Heinrichstrasse 28, A-8010 Graz, Austria.
Fabian
Walter M. F.
WM