In common with the homologous 3,3-difluoro- and 3,3,3-trifluoro-species, 3-fluoro-1,2-epoxypropane is a small chiral molecule with a simple rotational spectrum, making it potentially useful for chiral analysis via conversion of enantiomers into spectroscopically distinct diastereomers through formation of noncovalently bound complexes. The rotational spectrum of 3-fluoro-1,2-epoxypropane (FO) and of its heterodimer with the argon atom are obtained, along with several isotopologues of each, using Fourier transform microwave spectroscopy from 5.6 to 18.1 GHz, and their structures determined. Surprisingly, the structure of 3-fluoro-1,2-epoxypropane-argon does not show a strong similarity to those previously determined for 3,3-difluoro-1,2-epoxypropane-argon and 3,3,3-trifluoro-1,2-epoxypropane-argon but instead is more analogous to that of propylene oxide-argon. Equilibrium structural parameters and mapped electrostatic potential surfaces obtained via quantum chemistry calculations are used in rationalizing this result.

The microwave rotational spectrum of the gas-phase heterodimer formed between glycidol and the argon atom is measured from 5.6 to 18.1 GHz. Despite the existence of two low energy conformers for the glycidol molecule, the spectrum of only one argon-glycidol complex is observed, corresponding to the global minimum energy structure. Higher energy isomers, and indeed less abundant isotopologues of the observed species, are presumably not produced with sufficient number density to be detected under the conditions of the experiment. The spectroscopic constants obtained from the analysis of the spectrum are combined with ab initio quantum chemistry predictions for the dipole moment components to determine the structure of the lowest energy arrangement for argon-glycidol. This structure is compared with those previously observed for the argon complexes of analogous fluoromethyloxirane molecules. (C) 2020 Elsevier Inc. All rights reserved.