Vibrational Spectra of Hexafluorobutadiene-1,3

Abstract

The infrared absorption spectrum of gaseous CF2:CF–CF:CF2 has been obtained with a Perkin-Elmer double-pass spectrometer equipped with prisms of LiF, NaCl, and CsBr. The Raman spectrum of the compound in the liquid state, at 20°C and —120°C, was photographed with a 3-prism spectrograph of linear dispersion 15 A/mm at 4358 A. Polarization ratios were measured for the stronger bands. Weakly exposed Raman spectra were obtained of the compound in the gaseous state at room temperature and in the crystalline state at —160°C. The spectral data are inconsistent with the assumption of the molecular symmetry C2h (trans-form), but can be interpreted satisfactorily on the basis of symmetry C2v (cis-form). However, the data do not exclude the possibilities that the molecular symmetry is C2 or that the compound consists of a mixture of molecules of different symmetries. All of the 24 fundamental vibration frequencies have been assigned, and the spectra have been interpreted in detail. Some peculiarities in the spectra and some uncertainties in their interpretation are pointed out.