Ab Initio Calculations on Fluoroethanes:  Geometries, Dipole Moments, Vibrational Frequencies, and Infrared Intensities

Ab initio calculations have been performed at the MP2/6-31G** level for the series of fluorinated ethanes, C2HnF6-n, n = 0−5. The resulting geometries, dipole moments, vibrational frequencies, and absolute infrared intensities are reported for stable conformers of the series, including both anti and gauche species, together with their energy differences, for 1,2-difluoroethane, 1,1,2-trifluoroethane, and 1,1,2,2-tetrafluoroethane. The results are compared to available experimental data. In particular, because of the importance of members of this series as potential CFC substitutes, the accuracy of the computational results for infrared frequencies and intensities is discussed, including the dependence on basis set, for calculations at the MP2 level of the theory.