title: FT-IR and FT-Raman spectra of 6-chlorouracil: molecular structure, tautomerism and solid state simulation. A comparison between 5-chlorouracil and 6-chlorouracil.
abstract: A Raman and IR study of the biomolecule 6-chlorouracil was carried out in the solid state. The unit cell found in the crystal was simulated as a tetramer form by density functional calculations. Specific scale factors and scaling equations deduced from uracil molecule were employed in the predicted wavenumbers of 6-chlorouracil. The scaled wavenumbers were used in the reassignment of the IR and Raman experimental bands. Good reproduction of the experimental wavenumbers is obtained and the % error is very small in the majority of cases. A comparison between the molecular structure and charge distribution of 6-chlorouracil and 5-chlorouracil molecules was presented. The effect of the hydration with the PCM model in the molecular structure and charges was discussed. The optimum tautomers of 6-chlorouracil were optimized and analyzed. Six of them were related to those of uracil molecule. The effect of the halogen substitution in the sixth position of the pyrimidine ring in the stability of the different tautomers was evaluated. HOMO and LUMO orbital energy analysis were carried out.
authors.affiliation: Departamento de Química-Física-I, Facultad de Ciencias Químicas, UCM, Madrid 28040, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Ortiz
authors.affiliation: Departamento de Química-Física-I, Facultad de Ciencias Químicas, UCM, Madrid 28040, Spain.
authors.forename: M C
authors.initials: MC
authors.lastname: Alvarez-Ros
authors.affiliation: Departamento de Química-Física-I, Facultad de Ciencias Químicas, UCM, Madrid 28040, Spain. Electronic address: alcolea@quim.ucm.es.
authors.forename: M Alcolea
authors.initials: MA
authors.lastname: Palafox
authors.affiliation: R.D. Foundation Group of Institutions, NH-58, Kadrabad, Modinagar, Ghaziabad, India; Indian Spectroscopy Society, KC-68/1, Old Kavinagar, Ghaziabad 201 002, India. Electronic address: v_krastogi@rediffmail.com.
authors.forename: V K
authors.initials: VK
authors.lastname: Rastogi
authors.affiliation: Department of Physics, Arignar Anna Government Arts College, Musiri, Tiruchirappalli 621211, India.
authors.forename: V
authors.initials: V
authors.lastname: Balachandran
authors.affiliation: Indian Spectroscopy Society, KC-68/1, Old Kavinagar, Ghaziabad 201 002, India.
authors.forename: S K
authors.initials: SK
authors.lastname: Rathor
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D003460:Crystallization; D019281:Dimerization; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008968:Molecular Conformation; D016011:Normal Distribution; D013055:Spectrophotometry, Infrared; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D014498:Uracil / Q000031:analogs & derivatives* / Q000737:chemistry*
chemical_list: C044976:6-chlorouracil; D014498:Uracil; C010889:5-chlorouracil
keywords: 5-Chlorouracil; 6-Chlorouracil; 6-Halouracil derivatives; Mutagenicity; Raman spectra; Tautomerism