Vapour pressures, enthalpies and Gibbs energies of formation and sublimation of fluorene-2-carboxaldehyde

Abstract

This work presents a comprehensive experimental and computational study of the thermodynamic properties of fluorene-2-carboxaldehyde. The crystal vapour pressures of this compound were measured between (335.16 and 355.09)K, using the Knudsen mass-loss effusion method. From these results the standard molar enthalpies, entropies and Gibbs energies of sublimation were derived. The standard molar enthalpy of formation in the crystalline phase at the temperature 298.15K was derived from the standard molar energy of combustion, determined from combustion calorimetry measurements. This result was combined with the enthalpy of sublimation yielding the standard molar enthalpy of formation in the gaseous phase at T=298.15K, that was also derived from a computational study at the G3 and G4 levels. Theoretical calculations were also used to calculate heat capacity and entropy results in the gaseous phase. The enthalpy and temperature of fusion were determined from DSC experiments. From the thermodynamic properties of fusion and sublimation, those of vaporization were derived.The thermodynamic stability of fluorene-2-carboxaldehyde in the crystalline and gaseous phases was evaluated determining the standard Gibbs energies of formation, at the temperature 298.15K, and compared with the ones reported in the literature for fluorene.