Knowledge Bank

The infrared and Raman spectra of 1,1,2-trifluoroethane have been recorded, and conformers exhibiting $C1$ and $CS$ symmetries have been identified. For the gas phase, the temperature dependence of the intensities of selected Raman lines indicates that the $C1$ conformer is more stable by $1.6\pm 0.2$ kcal/mole. The torsional vibration for this conformer gives rise to $\Delta v=1$ Q branches at 121, 117, 113, 109.5, 106, 101, and $96cm-1$ in the far infrared spectrum. Interestingly, the $CS$ conformer is more stable by $1.02\pm 0.04$ kcal/mole in the liquid phase, and this conformer is the only one which exists in the crystalline solid state. The vibrational assignments for both conformers and factors affecting their relative stabilities will be discussed.