A study of the internal vibrations of 2.4.5-trimethoxybenzaldehyde is presented. The optimized geometry, harmonic vibration frequencies and intensities in IR and Raman spectra of the molecule were calculated by using B3LYP and 6-311G(d) basis set and assuming CS symmetry. We show the experimental FT-Raman and FT-IR spectra of the title compound measured in the range 100-3500 cm-1 and 500-3500 cm-1, respectively. The functional B3LYP and the basis set 6-311G(d) presents minimum energy training and led a result of the frequencies very close to the experiment, the agreements with experimental results being around 95%. The small difference between experimental and calculated modes has been interpreted by intermolecular interactions in the crystal. Discrepancies found from the experiment of a few cm-1 are acceptable compared to what is generally accepted in the literature.

FT-Raman, FT-IR, DFT, 2.4.5-trimethoxybenzaldehyde