Vibrational Analysis of the Ground States of Trifluoroacetyl Fluoride and Trifluoroacetyl Chloride

The vibrational frequencies, normal modes of vibration, and force constants of CF3COF and CF3COCl are calculated using the MP2/6-31G(d‘) method. Our calculations agree with those of Pacansky et al. in showing that the values of the ν6, ν7, ν8, ν12, and ν13 experimental frequencies of CF3COF need to be reassigned. Our calculations also show that the same experimental frequencies in CF3COCl need to be reassigned. The calculated force constants are improved by fitting them to the reassigned experimental vibrations. The simple descriptions of vibrational motion previously given are shown to be inaccurate for most vibrations.