Microwave Spectrum and Molecular Structure of 3-Fluoro-1,2-epoxypropane and the Unexpected Structure of Its Complex with the Argon Atom.

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.