Abstract
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 (ε=2.21), acetonitrile (ε=38), and in water (ε=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.
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Yekeler, H. Ab initio study on tautomerism of 2-thiouracil in the gas phase and in solution. J Comput Aided Mol Des 14, 243–250 (2000). https://doi.org/10.1023/A:1008132202838
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DOI: https://doi.org/10.1023/A:1008132202838