Microwave Spectra and Structures of Difluoroethylenes

摘要

The microwave spectra of the C12and C13species ofcishyphen;difluoroethylenehyphen;d1andcishyphen;difluoroethylenehyphen;d2have been investigated in the region of 8ndash;36 kMc. Effective rotational constants for the ground vibrational state have been determined and are combined with previous microwave data to obtain the structural parameters:rCC=1.324 Aring;,rCH=1.089 Aring;,rCF=1.335 Aring;, ang;FCC=122.1deg;, ang;HCC=124.0deg;.The microwave spectrum of vinylidene fluoride has been reinvestigated and the rotational constants for C13species obtained. These data lead to a structure:rCC=1.315 Aring;,rCH=1.079 Aring;,rCF=1.323 Aring;, ang;FCF=109.1deg;, ang;HCH=121.8deg;.A comparison of the structures with data for vinyl fluoride and ethylene shows that fluorine substitution produces a systematic shortening of both the CC and CF bonds.