Normal-mode vibrational frequencies and thermodynamic properties of uracil and 4-hydroxyuracil

✍ Scribed by Masayuki Shibata; Theresa Julia Zielinski; Robert Rein

• Publisher: John Wiley and Sons
• Year: 1980
• Tongue: English
• Weight: 326 KB
• Volume: 18
• Category: Article
• ISSN: 0020-7608
• DOI: 10.1002/qua.560180146

✦ Synopsis

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__ for U ⇄ U* of 1.06 e.u./mol by standard statistical thermodynamic equations. Δ__G__ is then 6.29 kcal/mol in the gas phase for U ⇄ U*. The reaction field continuum model of solvent effect lowers Δ__G__ to 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.