The Raman (2000 to 10 cm −1) and infrared (2000 to 30 cm −1 spectra of both the gaseous and solid phases of fluorodichloroacetyl chloride, CCl 2FCClO, have been recorded. In addition, the Raman spectrum of the liquid, along with qualitative depolarization ratios, has been obtained. These data have been interpreted on the basis of an equilibrium between the gauche and trans conformers (fluorine atom trans to the chlorine atom of the CClO top) in the gaseous and liquid phases. From the study of the Raman spectrum of the liquid at different temperatures, a value of 110 + 24 cm −1 (316 ± 68 cal mol −1) was determined for ΔH with the trans conformer being the more stable form. A similar study of the sample dissolved in liquid xenon gave a ΔH value of 177 + 14 cm −1 (506 ± 40 cal mol −1), again with the trans rotamer the more stable conformer. Therefore, the trans conformer is the predominate rotamer in the gas and liquid, and the only conformer present in the annealed solid. A complete vibrational assignment is proposed for both conformers based on infrared band contours, Raman depolarization data, group frequencies, and normal coordinate calculations. Optimized geometries, conformational stabilities, unscaled and scaled vibrational frequencies, and harmonic force fields are reported for both conformers from ab initio calculations utilizing the RHF 3-21 G∗ , RHF 6-31 G∗ and/or MP2 6-31 G∗ basis sets. These results are compared with the corresponding results for some similar molecules.