Valence force fields for the difluoroethylenes

Normal coordinate calculations of cis- and trans-CHFCHF and of CF2CH2 have been undertaken using Modified Valence Force Fields based on vibrational data of all the hydrogen and deuterium isotopes. A definite vibrational assignment is given for CF2CH2 based on new infrared and Raman gas phase spectra. The calculated valence force fields of cis- and trans-difluoroethylene. vinylidene fluoride and the vinyl halides mutually agree very well.