Chirality induction and amplification in the 2,2,2-trifluoroethanol⋅⋅⋅propylene oxide adduct.

Chirality induction and amplification in a model system, that is, the 2,2,2-trifluoroethanol (TFE)⋅⋅⋅propylene oxide (PO) adduct, were investigated using free-space and cavity-based Fourier transform microwave spectroscopy, complemented with high level ab initio calculations. Rotational spectra of four out of eight predicted TFE⋅⋅PO adducts were assigned, and the remaining four were shown to relax to the geometries of the four observed in a jet expansion. The g+ TFE⋅⋅⋅S-PO adduct was found to be favored over that of g- TFE⋅⋅⋅S-PO by a factor of 2.8 at 60 K. This difference contrasts the TFE dimer for which an extreme case of chirality synchronization was previously reported. All TFE⋅⋅⋅PO conformers observed take on the open arrangement, in contrast to 2-fluoroethanol⋅⋅⋅PO, which prefers the closed arrangement. Furthermore, perfluorination at CH3 increases the hydrogen-bonding energy by about 70 % over its ethanol counterpart.