Calorimetric and computational study of 7-hydroxycoumarin

The standard (p° = 0.1 MPa) molar energy of combustion in oxygen, at T = 298.15 K, of 7-hydroxycoumarin was measured by static bomb calorimetry. The value of the standard molar enthalpy of sublimation was obtained by Calvet microcalorimetry and corrected to T = 298.15 K. Combining these results, the standard molar enthalpy of formation of the compound, in the gas phase, at T = 298.15 K, has been calculated, −(337.5 ± 2.3) kJ · mol−1. The values for the temperature of fusion, Tfusion, and for the fusion enthalpy, at T = Tfusion, are also reported.Additionally, high-level density functional theory calculations using the B3LYP hybrid exchange-correlation energy functional with extended basis sets, the MC3BB and MC3MPW methods and more accurate correlated computational techniques of the MCCM suite have been performed for the compound.The agreement between experiment and theory gives confidence to estimate the enthalpy of formation of the remaining hydroxycoumarins substituted in the benzene ring.

► Experimental standard molar enthalpies of formation, sublimation of 7-hydroxycoumarin.
► Combustion calorimetry, sublimation microcalorimetry, differential scanning calorimetry.
► DFT calculations, MC3BB and MC3MPW methods have been performed for the compound and its isomers.
► Computational estimation of enthalpies of formation of 5-, 6-, and 8-hydroxycoumarin.