The microwave spectra, bromine nuclear electric quadrupole coupling tensor, and structure of 3-bromo-3,3-difluoropropene

► 3-Bromo-3,3-difluoropropene incorporated into a supersonic argon expansion. ► Pure rotational spectra recorded with chirped pulse Fourier transform microwave spectroscopy. ► Rotational and bromine hyperfine constants determined. ► Calculations reveal information regarding molecular structure. 3-Bromo-3,3-difluoropropene was seeded within a pulsed, supersonic expansion of argon gas. In this state, the microwave spectrum of the title molecule was recorded between the limits of 7.8 GHz and 14.2 GHz using a chirped pulse Fourier transform microwave spectrometer. Only the gauche conformer was observed in this study. A total of 1073 transitions have been recorded, 550 for the 79Br isotopologue and 523 for the 81Br isotopologue. The resolution of the technique, and the variety of transitions measured, has allowed the complete bromine quadrupole coupling tensors to be determined. These are reported together with the rotational spectroscopic parameters. Ab initio calculations have yielded a structure reproducing the experimental rotational constants.