Structural and conformational properties of 1,1,1-trifluoro-2-propanol investigated by microwave spectroscopy and quantum chemical calculations.

The microwave spectrum of 1,1,1-trifluoro-2-propanol, CF(3)CH(OH)CH(3), and one deuterated species, CF(3)CH(OD)CH(3), have been investigated in the 20.0-62.0 GHz spectral region at about -50 degrees C. The rotational spectrum of one of the three possible rotameric forms was assigned. This conformer is stabilized by an intramolecular hydrogen bond formed between the hydrogen atom of the hydroxyl group and the nearest fluorine atoms. The hydrogen bond is weak and assumed to be mainly a result of attraction between the O-H and the C-F bond dipoles, which are nearly antiparallel. The identified rotamer is at least 3 kJ/mol more stable than any other rotameric form. Two vibrationally excited states belonging to two different normal modes were assigned for this conformer, and their frequencies were determined by relative intensity measurements. The microwave work has been assisted by quantum chemical computations at the MP2/cc-pVTZ and B3LYP/6-311++G** levels of theory, as well as by the infrared spectrum of the O-H stretching vibration.