VIBRATIONAL STUDIES, BARRIER HEIGHT AND THERMODYNAMIC FUNCTIONS FOR BIOMOLECULES - 5-TRIFLUOROMETHYL URACIL

Laser Raman (50-4000 cm-1) and IR (200-4000 cm-1) spectra of 5-trifluo romethyl uracil have been recorded and analysed. It has been possible to assign all the 39 (26a'+ 13a'') normal modes of vibration. Consiste nt assignments have been made for the internal modes of the CF3 group, especially for the antisymmetric CF3 stretching and bending modes. Us ing thus assigned vibrational frequencies and assumed structural param eters, thermodynamic functions, in the temperature range 100-1000 K, h ave been computed and the barrier to the internal rotation for the CF3 top has been determined.