Intrahydrogen Bonding and Transition States Between Enol and Enethiol Tautomers in β-Thioxoketones
Bahjat A. Saeed, Rita S. Elias and Ebraheem Abdu Musad
DOI : 10.3844/ajassp.2011.762.765
American Journal of Applied Sciences
Volume 8, Issue 8
Problem statement: Hydrogen bonding is one of the most important concepts in chemistry because it is crucial to understand many different interactions both in gas phase and in condensed media. A particular subset is presented by the intramolecular hydrogen bonds where two ends of the same molecule interact, resulting in a ringlike structure. Approach: The study involved theoretical investigation of proton transfer and transition states in β-thioxoketones. Both structures of the enol and enethiol tautomers of β-thioxoketones were geometrically optimized then the transition states were obtained. The calculations were done at the B3LYP hybrid and 6-31G(d,p), 6-31+G(d,p), 6- 31++G(d,p), 6-311G(d,p), 6-311+G(d,p) and 6-311++G(d,p) basis sets. Results: The calculated energies of the enethiol tautomer are higher than those of the enol tautomer for all the thioxoketones studied in this work. The S...O distances are in the order: enethiol > enol > transition state in addition the hydrogen bonding in the enol tautomer is stronger than that in the enethiol tautomer. Conclusion: The interconversion within the tautomeric mixture in these compounds is preferable in the enethiol → enol direction.
© 2011 Bahjat A. Saeed, Rita S. Elias and Ebraheem Abdu Musad. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.