Ab initio SCRF study of the tautomeric equilibrium of 2-thiopyrimidine

Ab initio SCRF calculations have been carried out for the prototropic tautomerism of 2-thiopyrimidine (2TP) in gas phase and in solution. In the gas phase the thiol tautomer is the more stable species in keeping with the reported IR spectra in isolated matrices. In polar solvents the thione tautomer becomes more stabilized. The calculated tautomerism free energy changes for 2TP in the gas phase, cyclohexene dimethylsulfoxide and water are 8.165, 5.906, −5.513 and −5.829 kcal/mol, respectively.