A theoretical study of solvent effects on tautomeric equilibrium of 2,6-dimercaptopyridine

In the present paper, ab initio calculations have been performed for the thione-thiol tautomeric equilibrium of 2,6-dimercaptopyridine in the gas phase and in different solutions at HF/6-31G** level. The solvent effects on the tautomeric equilibrium are investigated Onsager self-consistent reaction field (SCRF) model. The results obtained show that the dielectric media have more significant effects on the molecular geometry of the thione tautomer than on that of the thiol tautomer, and the calculated tautomerism energies predict the thiol tautomer to be dominant in the gas phase and in solvents of low dielectric constant, however, owing to the strong polarization effects, in solvents of high dielectric constant, the tautomeric equilibrium is shift in favor of the more polar thione form, which are in agreement with experiment.