FT-IR and FT-Raman spectra of 5-fluoroorotic acid with solid state simulation by DFT methods

•All the tautomers of 5-fluoroorotic acid were described and analyzed.•The Raman and IR spectra of 5-fluoroorotic acid in the solid state were simulated.•The solid state simulation was carried out by a dimer and tetramer forms.•The characteristic skeletal modes in the low wavenumber range were determined.•The solid state scaled values are in good accordance to the experimental ones.

FT-Raman and FT-IR studies of the biomolecule 5-fluoroorotic acid in the solid state were carried out. The unit cell found in the crystal was simulated as a tetramer form by density functional calculations. They were performed to clarify wavenumber assignments of the experimental observed bands in the spectra. Correlations with the molecule of uracil were made, and specific scale equations were employed to scale the wavenumbers of 5-fluoroorotic acid. Good reproduction of the experimental wavenumbers is obtained and the % error is very small in the majority of the bands. This fact confirms our simplified solid state model. The molecular structure was fully optimized using DFT and MP2 methods. The relative stability of both the syn and anti conformations was investigated, and the anti-form was found to be slightly more stable, by 7.49 kJ/mol at the MP2 level. The structures of all possible tautomeric forms were determined. The keto-form appeared as the most stable one. The NBO atomic charges and several thermodynamic parameters were also calculated.

Graphical abstractSolid state simulation of 5-fluoroorotic acid.Figure optionsDownload full-size imageDownload as PowerPoint slide