Exploring C–H···O hydrogen bonds in dihydrocoumarin from combined vibrational spectroscopy and DFT calculations

The complete vibrational spectra assignment of dihydrocoumarin is performed through a combined vibrational spectroscopy and DFT calculations approach. To provide effective information, vibrational analysis was also performed for α-pyrone and coumarin related systems. The presence of extra components in the νC O band profile can only be understood by both Fermi resonance and monomer/dimer equilibrium phenomena, the latter established by C–H···O hydrogen bond with Δ H ° value of −8.4 ± 0.9 kJ mol −1 . The analysis of the ν C–H region indicates that both the methylene and aromatic C–H groups have a significant contribution to the formation of C–H···O bonded dimers in liquid dihydrocoumarin.