The microwave spectra and molecular structures of the chiral and achiral rotamers of 2,3,3-trifluoropropene and their gas-phase heterodimers with the argon atom

Abstract

The microwave spectra of two rotamers, connected by rotation of the –CHF2 group, of 2,3,3-trifluoropropene and all three of the singly substituted 13C isotopologues of each are obtained in the 5.6 – 18.1 GHz region using broadband chirped pulse Fourier transform microwave spectroscopy. The lower energy rotamer, stabilized by a weak intermolecular hydrogen bond, is chiral, existing as a pair of enantiomers, while the higher energy isomer, lacking this interaction but having a plane of symmetry, is achiral. Heterodimers of both rotamers with the argon carrier gas are also observed in the broadband spectrum and further analyzed using spectra obtained from 5.0 to 20.6 GHz with a Balle-Flygare cavity Fourier transform microwave spectrometer. Although all singly substituted 13C isotopologues are observed, in addition to the normal species, for the argon complex with the lower energy rotamer, only a single isotopologue of the argon complex, the parent, is observed with the higher energy rotamer. Despite differing slightly in detail, the argon atom occupies a similar position in the heterodimer with each rotamer, one that is also similar to the location of the argon atom in argon-2,3,3,3-tetrafluoropropene.