Ab initio computations of harmonic frequencies for the three isomeric difluorobenzenes have been carried out using the MO technique with split valence 3–21 G basis set. The computed frequencies have been compared with the experimental frequencies. The computed frequencies have been scaled with empirical scale factors in order to correct for the systematic errors originating in the limitations of the theoretical model. It was found necessary to use different scaling factors for the planar and non-planar modes.
