Conformational dynamics of 1-phenyl-2,2,2-trifluoroethanol by rotational spectroscopy and ab initio calculations

The rotational spectrum of 1-phenyl-2,2,2-trifluoroethanol, a chiral organic alcohol, was investigated using two chirped pulse Fourier transform microwave spectrometers. The molecule is a derivate of 2,2,2-trifluoroethanol, and the phenyl substitution plays a major role in altering the conformational landscape. Three equilibrium minima were identified at the MP2 and B3LYP-D3BJ levels of theory, of which only two exist as stable conformers after applying harmonic zero-point-energy correction. Rotational spectra of the most stable conformer and its eight C-13 isotopologues were assigned and the rotational constants obtained were used to refine the ab undo structure. The second conformer was not observed experimentally, and subsequent analysis indicates that the conformational conversion barrier was too low to trap this second conformer, even in a helium jet expansion. (C) 2018 Elsevier Inc. All rights reserved.