Knowledge Bank

A complete assignment of the vibrational fundamentals of perfluorocyclopropene is proposed. It is based on the Raman spectrum of the liquid, on infrared spectra under a variety of conditions, and on zero-order normal coordinate calculations. The fundamentals for this $C2v$ molecule are (in $cm-1$): $(a1)$ 1940, 1367, 929, 709, 509, 245; $(a2)$ 616, 214; $(b1)$ 1331, 892, 781, (250); $(b2)$ 1109, 351, 251. An overlay normal coordinate calculation for $3,3-difluorocyclopropene,1$ $1,3,3-trifluorocyclopropene,2$ and perfluorocyclopropene has yielded a vibrational potential function for these molecules. All force constants except those for CC stretching were fit to more than one molecule. The various CC stretching constants show an interesting pattern of strong influence of the position of fluorine substitution.