FTIR, FT-Raman, FT-NMR and quantum chemical investigations of 3-acetylcoumarin.

3-Acetylcoumarin (3AC) was synthesised by a Knoevenagel reaction. Conformational analysis using the B3LYP method was also carried out to determine the most stable conformation of the compound. FTIR and FT-Raman spectra of 3AC have been recorded in the range 4000-400 and 4000-100 cm(-1), respectively. (1)H and (13)C NMR spectra have also been recorded. The complete vibrational assignment and analysis of the fundamental modes of the compound were carried out using the experimental FTIR and FT-Raman data and quantum mechanical studies. The experimental vibrational frequencies were compared with the wavenumbers obtained theoretically from the DFT-B3LYP/B3PW91 gradient calculations employing the standard 6-31G(**), high level 6-311++G(**) and cc-pVTZ basis sets for optimised geometry of the compound. The frontier molecular orbital energies of the compound are determined by DFT method.