RAMAN AND FAR-INFRARED SPECTRA, STRUCTURAL PARAMETERS, AND AB-INITIO CALCULATIONS ON ACETYL-CHLORIDE

The Ramam spectra (3100-10 cm-1) of gaseous, liquid and solid acetyl c hloride (CH3CClO) and acetyl-d3 chloride (CD3CClO) were recorded and q ualitative depolarization values were obtained for the liquid. Additio nally, the infrared spectra (3100-50 cm-1) of the gas and solid were r ecorded. A complete vibrational assignment is proposed for both isotop omers. The assignments are supported by normal coordinate calculations utilizing force constants from the ab initio calculations. The methyl torsion is observed at 162.8 cm-1 from which a threefold barrier of i nternal rotation of 622 cm-1 (1779 cal mol-1) is calculated. Utilizing the frequencies for the isolated C-H stretching frequencies from the CHD2CClO molecule, r0 parameters of 1.093 and 1.096 angstrom were obta ined for the C-H(s) and C-H(a) bond distances. The heavy atom r0 struc tural parameters were obtained from previously reported rotational con stants from ten isotopomers. Ab initio calculations were carried out e mploying the RHF/3-21G, RHF/6-31G* and MP2/6-31G* basis sets to obtai n the vibrational frequencies, force constants, infrared and Raman int ensities, structural parameters and barriers to internal rotation. The theoretical results were compared with the experimental quantities wh en appropriate.