RAMAN AND FAR-INFRARED SPECTRA, CONFORMATIONAL STABILITY AND AB-INITIO CALCULATIONS FOR OXALYL FLUORIDE

The Raman (2000-20 cm(-1)) and far-infrared (110-35 cm(-1)) spectra of gaseous oxalyl fluoride, (CFO)(2), have been recorded. The internal t orsional mode of the trans conformer has been observed at 42.5 cm(-1), with several excited states falling to lower wavenumber, Two conforme r pairs have been used to experimentally determine the Delta H value f rom the temperature dependence of the Raman spectrum of the gas. One p air is observed at 1892 and 1869 cm(-1), which are assigned to the C=O stretches of the cis and trans conformers respectively, from which a Delta H value of 302 +/- 69 cm(-1) (863 +/- 196 cal mol(-1)) was deriv ed. Similarly, a value of 250 +/- 55 cm(-1) (710 +/- 158 cal mol(-1)) was determined from the conformer pair observed at 825 and 803 cm(-1), which are assigned to the CFO bend and the carbon-carbon stretch of t he cis and trans conformers respectively. A complete vibrational assig nment is proposed for both conformers based on depolarization values, relative intensities and normal coordinate calculations. Optimized str uctural parameters, conformational stabilities, barriers to internal r otation, scaled and unsealed vibrational wavenumbers and harmonic forc e fields are reported for both conformers from ab initio gradient calc ulations utilizing the RHF/3-21G, RHF/631G and MP2/6-31G* basis sets. The results are compared with the corresponding quantities obtained f or some similar molecules.