Ab initio calculations of vibrational frequencies, potential functions of internal rotations and vibrational infrared and Raman spectra for 3,3,3-trifluoropropanal

The conformational behavior and structure of 3,3,3-trifluoropropal have been investigated by utilizing ab initio calculations with the 6-31G** basis set (valence double zeta basis with polarization functions on all atoms) at the restricted Hartree Fock (RHF), second-order Møller-Plesset perturbation (MP2), and Density Functional (B3LYP) levels. The molecule is predicted to have a cis ⇔ gauche conformational equilibrium. Full optimization of the transition states was performed and the rotational barriers of both the CHO and CF₃ rotors were calculated. Vibrational frequencies were computed at the three levels and the zero-point corrections were included into the calculated asymmetric CHO rotational barrier. Complete vibrational assignments were made on the basis of normal coordinate calculations for both stable conformers of the molecule.