Vibrational spectroscopy investigation using ab initio and density functional theory analysis on the structure of 3,4-dimethylbenzaldehyde

The FT-IR and FT-Raman spectra of 3,4-dimethylbenzaldehyde (3,4-DMB) has been recorded in the region 4000-400 and 3500-100 cm−1, respectively. The optimized geometry, frequency and intensity of the vibrational bands of 3,4-DMB were obtained by the ab initio and DFT levels of theory with complete relaxation in the potential energy surface using 6-311G(d,p) basis set. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FT-IR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The experimental spectra also coincide satisfactorily with those of theoretically constructed bar type spectrograms.