NATURAL SCIENCES

Journal of fundamental
and
applied researches

System analysis of model calculations of structure and spectra of dihydroxy tautomer 5X-uracil

2013. №3, pp. 115-121

Elkin Mihail D. - D.Sc. (Physics and Mathematics), Professor, Astrakhan State University, 20a Tatishchev Str., Astrakhan, 414056, Russian Federation, elkinmd@mail.ru

Smirnov Vladimir V. - D.Sc. (Pedagogy), Associate Professor, Astrakhan State University, 20a Tatishchev Str., Astrakhan, 414056, Russian Federation, kof@aspu.ru

Dzhalmuhambetova Elena A. - Ph.D. (Physics and Mathematics), Associate Professor, Astrakhan State University, 20a Tatishchev Str., Astrakhan, 414056, Russian Federation, kof@aspu.ru

Alykova Olga M. - Ph.D. (Pedagogy), Associate Professor, Astrakhan State University, 20a Tatishchev Str., Astrakhan, 414056, Russian Federation, kof@aspu.ru

Grechukhina Oksana N. - Ph.D. (Physics and Mathematics), Associate Professor, Astrakhan State University, 20a Tatishchev Str., Astrakhan, 414056, Russian Federation, kof@aspu.ru

Gaysina Alfiya R. - Assistant, Astrakhan State University, 20a Tatishchev Str., Astrakhan, 414056, Russian Federation, kof@aspu.ru

Dihydroxy 5X-uracil (X = F, Cl, NH3) is one of the tautomer forms of substituted uracil. The work presents regularities of the shift of vibrational spectrum bands of the mentioned compounds, defines its spectrum identification characteristics of their possible conformers. We have considered four models of conformers that are determined by the values of dihedral angles. We used DFT/B3LYP method with bases G-311G(p,d) and G-311+G(p,d) in calculating the optimized structure and vibrational frequencies. The difference in the value of geometrical parameters of the models does not exceed 0.008 ? for the lengths of valence bonds and 1.2? for bond angles. The difference in the intensity of spectrum bands in the range of 1400–1000 cm–1, and changes in the frequencies of torsional vibrations of OH-bonds can be used for identification of conformers. Influence of the substitute results in the band shift in the range of 1700–1000 cm–1 by ~ 30 cm–1, that enables us to make a conclusion about the local effect of the substitute on the force field of the uracil frame.

Key words: dihydroxy 5X-uracil,uracil,dimer,conformer,tautomer,vibrational spectra,anharmonic,adiabatic potential