Vibrational spectra of thiocarbonyl chlorofluoride and a normal coordinate analysis of thiocarbonyl chlorofluoride and thiocarbonyl difluoride

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Abstract
The previously unreported infrared and Raman spectra of thiocarbonyl chlorofluoride have been obtained and analyzed. An assignment has been made for the in-plane fundamental frequencies. The frequency of the out-of-plane fundamental has been obtained from a partial analysis of the near ultra-violet (π*n) system. Normal coordinate analyses for thiocarbonyl fluoride and thiocarbonyl chlorofluoride have been carried out using the Urey–Bradley potential field. The value of the CS stretching force constant is found to show a marked change with the halogen substitution in contrast to the CO stretching constant in the carbonyl halides. This is attributed to the presence of ionic valence bond structures in the thiocarbonyl halides which are not significant in the carbonyl halides.