VIBRATIONAL SPECTRA AND ASSIGNMENTS OF THE FUNDAMENTALS OF CIS-3,4-DIFLUORO-CYCLOBUTENE

1. N. C. Craig, S. E. Hawley, L. V. Lee and A. Pearson, Spectrochim. Acta 50A, 191 (1994). 2. N. C. Craig, S. E. Hawley and C. L. Perry, Spectrochim. Acta 47A, 881 (1991); E. M. Suzuki and JP. Nibler, Spectrochim. Acta 30A, 15 (1974).Author Institution: Oberlin College, Oberlin, OH 44074The cis isomer of 3,4-difluorocyclobutene is formed as a minor product in the reaction of gaseous cis-3,4-dichlorocyclobutene with solid ${AgF_{2}}^{1}.$ On a sample of only 0.1 mmol of cis-3,4-difluorocyclobutene gas-phase IR spectra and liquid-phase Raman spectra were recorded. For this molecule of $C_{s}$ symmetry, $\kappa = 0.49$, and the axis of the least moment of inertia, $I_{a}$, is perpendicular to the symmetry plane. Thus, $a^{\prime\prime}$ modes correspond to bands of A-type shape in the gas-phase infrared spectrum, whereas $a^{\prime}$ modes give bands of hybrid B/C shape. The assigned fundamentals are, in $cm^{-1}: (a^{\prime})$ 3102 (ave. of FR doublet), 2878, 1560, 1350, 1234, 1170, 1050, 998, 837, 769, 408 and 243; $(a^{\prime\prime})$ 3078, 2956, 1343, 1307, 1180, 1092, 1057, 954, 923, 588, 466 and 160. Frequencies in italics are liquid-phase observations; others are gas-phase values. Overall, the assignments correlate reasonably well with the assignments for the trans isomer and for cis-3,4-$dichlorocyclobutene.^{1,2}