Experimental and theoretical studies of the vibrations and structure of 2,2,2-trifluoroethyl trifluoroacetate, CF3CO2CH2CF3

The molecular structure of 2,2,2-trifluoroethyl trifluoroacetate, CF3CO2CH2CF3, has been determined in the gas-phase from electron-diffraction data supplemented by ab initio, (MP2) and DFT calculations using basis sets up to 6-311 ++G(d,p). Both experimental and theoretical data indicate that although both structures with anti, anti (C-s) and anti, gauche (C-1) conformations exist by rotating about the O-C(H-2) bond, the anti, anti structure is preferred. The difference in free energy was calculated to be 2.1 kJ mol(-1) (C-s conformer lower in energy) and as I he C, conformer has a double multiplicity relative to the C, conformer, the ratio of C-1-C-s conformer was predicted to be 0.41: 0.59. This conformational preference was studied using the total energy scheme and the natural bond orbital partition scheme. Additionally, the total potential energy has been deconvoluted using six-fold decomposition in terms of a Fourier-type expansion. Infrared spectra of CF3CO2CH2CF3 have been obtained for the gaseous, liquid and solid phases and the Raman spectrum for the liquid phase. Harmonic vibrational frequencies and a scaled force field have been calculated, leading to a final root-mean-square deviation of 7.3 cm(-1) (c) 2008 Elsevier B.V. All rights reserved.