A scaled quantum mechanical approach of vibrational analysis of o-tolunitrile based on FTIR and FT Raman spectra, ab initio, Hartree Fock and DFT methods

Abstract

The FTIR and FT Raman vibrational spectra of o-tolunitrile have been recorded using Perkin-Elmer 180 Spectrometer in the range 3100–100 cm −1. A detailed vibrational spectral analysis has been carried out and assignments of the observed fundamental bands have been proposed on the basis of peak positions and relative intensities. The optimized geometrical parameters, force constants, true rotational constants, rotational temperatures, Potential Energy Distribution (PED) and fundamental vibrational frequencies of the title compound were evaluated using Hartree Fock and Density Functional B3LYP methods with 6-31G(d) basis sets. The vibrational harmonic frequencies were scaled using scale factor which yielded a good agreement between observed and calculated frequencies. With hope of providing more and effective information on the fundamental vibrations, a normal co-ordinate analysis has been performed by assuming C s point group symmetry. The results of the calculations were applied to simulated Infrared and Raman spectra of the title compound which showed excellent agreement with the observed spectra.