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Computational study of tautomerism and aromaticity in mono‐ and dithio‐substituted tropolone
Author(s) -
Paine S. W.,
Salam A.
Publication year - 2012
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.24268
Subject(s) - tautomer , tropolone , chemistry , computational chemistry , polarizable continuum model , chemical shift , basis set , aromaticity , enol , gibbs free energy , keto–enol tautomerism , solvent effects , density functional theory , solvent , molecule , thermodynamics , stereochemistry , organic chemistry , physics , catalysis
Keto‐enol tautomerism in mono‐ and dithio‐substituted analogs of tropolone was investigated using electronic structure computations. Seven structural isomers of C 7 H 6 OS and four of C 7 H 6 S 2 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 4 n + 2 rule, and supported by nucleus independent chemical shifts computations of NMR chemical shifts in these seven membered cyclic systems. © 2012 Wiley Periodicals, Inc.