Vibrational spectra, normal coordinate analysis and thermodynamics of 2, 5-difluorobenzonitrile

Abstract

The FTIR spectrum of 2, 5-difluorobenzonitrile has been recorded in the region 200–4000 cm−1 (in liquid phase). The laser Raman spectrum in the range of 0–3500 cm−1 (in liquid phase) has also been recorded. The spectra have been analyzed assuming C s point group symmetry for the molecule. A zero-order normal coordinate analysis has been made for the molecule using force constants derived earlier. On the basis of potential energy distributions and eigen vectors unambiguous vibrational assignments have been made for all the fundamentals of the molecule. Thermodynamic functions have also been computed in the temperature range 200–1000 K by utilizing the observed fundamental frequencies assuming rigid-rotor harmonic oscillator approximation.