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- Title
COMPUTATIONAL STUDY OF THE KETO-ENOL TAUTOMERISM IN B-KETOAMIDES.
- Authors
Salazar-Rodríguez, Fausto A.; Mera-Grandas, Luis F.; Mujica-Martínez, Cesar A.
- Abstract
Tautomerism is a special type of isomerism involving the movement of an atom, resulting in changes in the molecular structure and properties of both isomers. One of the best-known tautomeric equilibria is the keto-enol, where carbonyl compounds, which have hydrogen atoms in their alpha carbons, quickly interconvert into their corresponding enols. Experimentally, the existence of different tautomeric forms can be studied by using mass spectrometry and nuclear magnetic resonance spectroscopy. ß-ketoamides are compounds that, in principle, have several tautomeric equilibria, but the most important is the keto-enol tautomerism. The relative amounts of the keto and enol isomers for these compounds, in polar solvents at various temperatures, were determined experimentally by NMR. However, these results were explained qualitatively in terms of steric effects and substituent groups. In this work, computational tools are used to quantify the different molecular parameters that favor the different tautomeric forms, as well as to obtain thermodynamic and kinetic parameters. Specifically, density functional theory is used to obtain equilibrium geometric structures, energetics, and thermodynamic parameters of the different tautomers and the transition state. The rate constants are determined through the Eyring-Polanyi equation. The character of the transition state and the synchronicity of the tautomerization process are determined by examining the relative variation of the bond indices. Results indicate an early transition state and an asynchronous tautomerization mechanism.
- Subjects
TAUTOMERISM; ISOMERS; CARBONYL compounds
- Publication
Journal of Research of the University of Quindio / Revista de Investigaciones Universidad del Quindio, 2019, Vol 31, p235
- ISSN
1794-631X
- Publication type
Abstract