Raman and infrared spectra, conformational stability, ab initio calculations and vibrational assignments for chlorodifluoroacetyl fluoride

✍ Scribed by Barry R. Drew; T. K. Gounev; Gamil A. Guirgis; J. R. Durig

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 393 KB
• Volume: 29
• Category: Article
• ISSN: 0377-0486
• DOI: 10.1002/(sici)1097-4555(199803)29:3<205::aid-jrs226>3.0.co;2-j

✦ Synopsis

The Raman spectra (2000-10 cm-1) of chlorodiÑuoroacetyl Ñuoride, in the liquid phase with qualit-CClF 2 CFO, ative depolarization ratios and the crystalline solid were recorded. The infrared spectra (2000-30 cm-1) of the vapor and solid phases were also obtained and additional spectra of the sample dissolved in liquid xenon were recorded at di †erent temperatures between Ô 100 and Ô55 ÄC. The data were interpreted in terms of an equilibrium between a gauche conformer which is predominant in the vapor and liquid phases and an anti (the chlorine atom is trans to the Ñuorine atom on the CFO moiety) conformer with only the gauche conformer present in the crystalline solid. From infrared band intensities of chlorodiÑuoroacetyl Ñuoride in xenon in the temperature range 173-213 K, taking into account intensity di †erences predicted from ab initio calculations, a value of DH = 422 » 40 cm-1 is estimated with the gauche conformer being the more stable form. Optimized geometries and conformational stabilities were derived from ab initio calculations at the levels of RHF/6-31G*, MP2/6-31G* and MP2/6-311 + G** with all of the calculations predicting the gauche rotamer to be the most stable form. The vibrational wavenumbers, harmonic force constants and infrared intensities were obtained from the MP2/6-31G* calculations, whereas the Raman activities and depolarization values were obtained from the RHF/6-31G* calculations. The spectra are interpreted in detail and the results are compared with those obtained for some related molecules.