DFT study of tautomerism in azirine and related systems

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.