Ab initio study on tautomerism of 2-thiouracil in the gas phase and in solution

Yekeler H.

JOURNAL OF COMPUTER-AIDED MOLECULAR DESIGN, vol.14, no.3, pp.243-250, 2000 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 14 Issue: 3
  • Publication Date: 2000
  • Doi Number: 10.1023/a:1008132202838
  • Page Numbers: pp.243-250


Ab initio geometry optimizations were carried out at the HF/3-21G and HF/6-31+G** levels for the six tautomeric forms of 2-thiouracil (2TU, 2TU1, 2TU2, 2TU3, 2TU4, 2TU5) in the gas phase and in solution. To obtain a more definitive estimate of the relative stabilities for 2-thiouracil tautomers in the gas phase, single-point MP2/6-31+G** calculations were performed on the HF/6-31+G** optimized geometries. The tautomeric equilibria in 1,4-dioxane (epsilon = 2.21), acetonitrile (epsilon = 38), and in water (epsilon = 78.54) were studied using the self-consistent reaction field (SCRF) theory. The calculated relative free energies indicated that 2TU is the energetically preferred tautomer in the gas phase and in solution. The stability order of 2-thiouracil tautomers depends on the level of theory and the dielectric constant of the solvent. The obtained results are compared with the available experimental data.