DFT study of tautomerism in azirine and related systems

Journal of Molecular Structure: THEOCHEM 956 (2010) 97–102

Hossein Tavakol *
Chemistry Department, Science Faculty, University of Zabol, Zabol, Iran

Abstract

calculations were applied to optimize the structures of tautomers and transition states in azirine, dihydroazete, dihydropyrrole and tetrahydropyridine at B3LYP/6-311++G** and B3LYP/AUG-CC-PVTZ levels of theory. Then, important molecular parameters, IR frequencies, and energetic results in the gas phase and three different solvents (cyclohexane, chloroform and DMSO) were extracted. The energetic results show that relative stability of enamine tautomer (versus imine tautomer) increases with the increase of ring size and calculated frequencies show that by decreasing ring size from 6-membered to 4-membered ring, the frequency of endocyclic double bonds decreases, but in 3-membered ring, substantial increasing is observed. As well as, the barrier energies of tautomerisms are very high and various solvents have a little effect of on kinetic and thermodynamic data.