Computational study of tautomerism and aromaticity in mono- and dithio-substituted tropolone
Article first published online: 10 JUL 2012
Copyright © 2012 Wiley Periodicals, Inc.
International Journal of Quantum Chemistry
Volume 113, Issue 9, pages 1245–1252, 5 May 2013
How to Cite
Paine, S. W. and Salam, A. (2013), Computational study of tautomerism and aromaticity in mono- and dithio-substituted tropolone. Int. J. Quantum Chem., 113: 1245–1252. doi: 10.1002/qua.24268
- Issue published online: 20 MAR 2013
- Article first published online: 10 JUL 2012
- Manuscript Accepted: 12 JUN 2012
- Manuscript Revised: 8 JUN 2012
- Manuscript Received: 29 FEB 2012
- electronic structure thiotropolone;
Keto-enol tautomerism in mono- and dithio-substituted analogs of tropolone was investigated using electronic structure computations. Seven structural isomers of C7H6OS and four of C7H6S2 were optimized fully in gas phase at HF and B3LYP theoretical levels in combination with the 6-311++g** basis set, as well as with the CBS-QB3 and G3 methods. To examine the effects of an aqueous solvent on tautomeric equilibrium constants, each species was optimized in water using the self-consistent reaction field polarizable continuum model at HF/6-311++g** and B3LYP/6-311++g** model chemistries. In both phases it was found that the enol forms were significantly more stable with respect to electronic energy and Gibbs free energy compared to the keto isomers, and outnumbered the keto species by several orders of magnitude. This was understood on the basis of elementary Hückel theory and the 4n + 2 rule, and supported by nucleus independent chemical shifts computations of NMR chemical shifts in these seven membered cyclic systems. © 2012 Wiley Periodicals, Inc.