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 (Cs) and anti, gauche (C1) conformations exist by rotating about the O-C(H2) bond, the anti, anti structure is preferred. The difference in free energy was calculated to be 2.1 kJ mol-1 (Cs conformer lower in energy) and as the C1 conformer has a double multiplicity relative to the Cs conformer, the ratio of C1:Cs 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.
|Number of pages||10|
|Journal||Journal of Molecular Structure|
|Publication status||Published - Jan 2009|
- 2,2,2-Trifluoroethyl trifluoroacetate
- Gas-phase electron diffraction
- Ab initio calculations
- DFT calculations
- Internal barrier to rotation
- Infrared and Raman spectroscopy
- PHASE ELECTRON-DIFFRACTION
- MOLECULAR-ORBITAL THEORY
- EQUILIBRIUM STRUCTURES
- CRYSTALLINE PHASES