A chirped pulse Fourier transform microwave study of the refrigerant alternative 2,3,3,3-tetrafluoropropene

Abstract

Fourier transform microwave, rotational spectra in the 6–18 GHz band of the low global warming potential, low ozone depletion potential refrigerant alternative, 2,3,3,3-tetrafluoropropene (HFO-1234yf), and in natural abundance, its three singly substituted 13C isotopologues are obtained using a newly constructed chirped pulse spectrometer. Employing anharmonic vibration–rotation interaction alpha constants from ab initio calculations, the rotational constants determined for the ground vibrational state of the molecule are corrected to provide equilibrium values of these constants for all four isotopologues. The equilibrium constants are used for structure determination via both Kraitchman substitution coordinates and least squares fits to equilibrium moments of inertia. Both experiment and theory give a structure in which all but two fluorine atoms in the terminal –CF 3 group are coplanar. A substantial barrier to internal rotation of this group is predicted by ab initio calculation, and no evidence of internal rotation is seen in the spectra. A detailed description of the new spectrometer is given.