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Normal‐mode vibrational frequencies and thermodynamic properties of uracil and 4‐hydroxyuracil
Author(s) -
Shibata Masayuki,
Zielinski Theresa Julia,
Rein Robert
Publication year - 1980
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560180146
Subject(s) - mindo , chemistry , moment of inertia , molecular vibration , normal mode , aqueous solution , solvent , thermodynamics , solvent effects , computational chemistry , vibration , molecule , physics , quantum mechanics , organic chemistry
Abstract Normal‐mode vibrational frequencies were obtained for uracil and 4‐hydroxyuracil with the MINDO /3 SCF method. MINDO /3 vibrational frequencies and the moments of inertia for STO ‐3G optimized geometries yielded a Δ S T 0for U ⇄ U* of 1.06 e.u./mol by standard statistical thermodynamic equations. Δ G T 0is then 6.29 kcal/mol in the gas phase for U ⇄ U*. The reaction field continuum model of solvent effect lowers Δ G T 0to 5.3 kcal/mol in aqueous solution. The tautomeric equilibrium constant in solution is then 1.3 × 10 −4 , in good agreement with experimental values.