Étude thermodynamique de l'acridone et de la thioxanthone

Abstract

In the present work we studied acridone and thioxanthone by combustion calorimetry of small amounts of substance, by sublimation calorimetry, by differential thermal analysis, and by heat capacity measurements. The thermodynamic quantities derived are as follows: For acridone: [Formula: see text] [Formula: see text] [Formula: see text] [Formula: see text] For thioxanthone: [Formula: see text] [Formula: see text] [Formula: see text] [Formula: see text] ΔfusHm = (35.50 ± 0.28) kJ mol−1, Ttp = (487.88 ± 0.02) K. The experimental results permitted us to determine for each molecule its resonance energy and to compare it with the theoretical value. This comparison fits well for acridone, which is planar. The difference observed in the case of thioxanthone shows that this molecule is not planar, in accord with literature structural results. From the experimental enthalpy of atomization of acridone, we determined an enthalpy value for the Cb—N bond. Using the enthalpy contributions previously determined in our laboratory, we found a value for the enthalpy of atomization of thioxanthone in accord with the experimental result. Keywords: thermodynamics; calorimetry; differential thermal analysis; acridone; thioxanthone; enthalpies of combustion, of sublimation, of fusion; resonance energy; enthalpies of atomization, of intramolecular bonds; triple point temperature.