The molecular structure and conformational properties of ethyl trifluoroacetate, CF3CO2CH2CH3, were determined in the gas phase by electron diffraction, and vibrational spectroscopy (IR and Raman). The experimental investigations were supplemented by ab initio (MP2) and DFT quantum chemical calculations at different levels of theory. Experimental and theoretical methods result in two structures with Cs (anti-anti) and C1 (anti-gauche) symmetries, the former being slightly more stable than the latter. The electron-diffraction data are best fitted with a mixture of 56% anti-gauche and 44% anti-anti conformers. The conformational preference was also studied using the total energy scheme, and the natural bond orbital scheme. Also, the infrared spectra of CF3CO2CH2CH3 are reported for the gas, liquid and solid states, as is the Raman spectrum of the liquid. The comparison of experimental averaged IR spectra of Cs and C1 conformers provides evidence for the predicted conformations in the IR spectra. Harmonic vibrational wavenumbers and scaled force fields have been calculated for both conformers.
- gas-phase electron diffraction
- DFT calculations
- internal barrier to rotation
- infrared and Raman spectroscopy
- AB-INITIO CALCULATIONS
- CRYSTALLINE PHASES