CONFORMATIONAL STABILITY, BARRIERS TO INTERNAL-ROTATION, VIBRATIONAL ASSIGNMENT, STRUCTURAL PARAMETERS, AND AB-INITIO CALCULATIONS OF OXALYL CHLOROFLUORIDE

The Raman spectra 2000-10 cm(-1)) of gaseous, liquid and solid oxalyl chlorofluoride, CFOCClO, have been recorded. The infrared spectra (200 0-20 cm(-1)) of the gas and solid have also been recorded. These data have been interpreted on the basis of an equilibrium between the trans (fluorine atom is oriented trans to the chlorine atom) and cis confor mers in the fluid phases, with the trans rotamer being the more stable form. A variable-temperature study of the infrared spectrum of the sa mple dissolved in liquid xenon gives an enthalpy difference of 201 +/- 94 cm(-1) (0.574 +/- 0.27 kcal mol(-1)). A similar variable-temperatu re study of the Raman spectrum of the liquid gives a conformational en thalpy difference of 461 +/- 70 cm(-1) (1.32 +/- 0.2 kcal mol(-1)). A complete vibrational assignment is provided based on group frequencies , and infrared and Raman spectral intensities, along with support from the normal coordinate analysis utilizing force constants from the ab initio calculations. Optimized geometries, conformational stabilities, unsealed and scaled vibrational frequencies, and harmonic force field s are reported for both conformers from ab initio calculations utilizi ng the RHF/3-21G, RHF/6-31G* and/or MP2/6-31G* basis sets. These resu lts are compared with the corresponding data obtained from both experi ment and theory for some similar molecules.