Infrared and Raman spectra, conformational stability, barriers to internal rotation, ab initio calculations and vibrational assignments for dichlorofluoroacetyl fluoride Original Research Article

The Raman (2000 to 10 cm−1) spectra of dichlorofluoroacetyl fluoride, CCl2FCFO, of the vapor, liquid with qualitative depolarization ratios and amorphous and crystalline states were recorded. The infrared (2000 to 50 cm−1) spectra of the vapor and solid phases were also obtained and additional spectra as a solute in xenon were recorded at different temperatures. The data have been interpreted in terms of an equilibrium between an anti (the two fluorine atoms being trans to each other) and a gauche conformer in the vapor and liquid phases, whereas only the anti conformer was present in the crystalline solid. From infrared band intensities of dichlorofluoroacetyl fluoride in xenon in the temperature range 173 to 213 K a value of ΔH = 289 ± 25 cm−1 (828 ± 72 cal/mol) was calculated with the anti conformer being the more stable form. Optimized geometrics and conformational stabilities were derived from ab initio calculations using the basis sets RHF/3-21G∗, RHF/6-31G∗ and MP2/6-31G∗, and all of the calculations predict the anti rotamer to be the most stable conformer. The vibrational frequencies were calculated using appropriate scaling factors, and the spectra are interpreted in detail. The results have been compared with those obtained for related molecules.