Vibrational assignments and a potential function for 3,3-difluorocyclopropene-d0, -d1, and -d2
Complete assignments of the vibrational fundamentals of 3,3-difluorocyclopropene and its d1 and d2 isotopic modifications are derived from infrared and Raman spectra. The 15 fundamentals for the undeuterated molecule are as follows, in cm-1: (a1) 3150, 1598, 1343, 946, 769, 500; (a2) 883, 393; (b1) 3128, 1131, 968, 522; (b2) 1094, 680, 416. An 18-parameter potential function is fit to the full set of frequencies for the three isotopic species. Contributions of internal coordinates to normal modes are analyzed in terms of potential energy distributions, and frequencies are correlated with those of the closely related molecules, CF2-N=N, CH2-CH=CH, CF2-CH=CF, and O=C-CH=CH. Changes in potential constants of ring bonds in going from unsubstituted molecules to fluorine-bearing ones correlate with changes in bond lengths. Interpretable CF bond characteristics are also found in these molecules. © 1978 American Chemical Society.