Vibrational assignments and electronic structure calculations for 3-acetylcoumarin

Laser Raman (3500–50 cm−1) and IR (4000–400 cm−1) spectral measurements have been made on the laboratory prepared solid 3-acetylcoumarin. Molecular electronic energy, equilibrium geometrical structure and harmonic vibrational spectra have been computed at the RHF/6-31G(d,p) and B3LYP/6-31G(d,p) levels of theory. A complete vibrational assignment aided by the theoretical harmonic frequency analysis has been proposed. The B3LYP/6-31G(d,p) geometrical parameters, and frequencies of the CO in the pyrone and acetyl group are in good agreement with experiment. The difference in the frequencies due to the two carbonyl groups, 50 cm−1, which is attributed to the conjugation effect, is accounted for by the B3LYP to be 56 cm−1.