Étude thermodynamique des acides phtalique, isophtalique et téréphtalique

Abstract

A thermodynamic study of phthalic, isophthalic, and terephthalic acids (general formula: C8H6O4) was carried out by sublimation calorimetry and differential thermal analysis. With values of combustion enthalpy taken from the literature, it was possible to determine their enthalpies of formation in the gaseous state and at 298.15 K and their resonance energy. The results enabled us to do a comparative study of the relative stability of the three acids, on the one hand, and of different benzene disubstituted derivatives, on the other hand. From the enthalpy of sublimation, it was possible to determine the energetic contribution of the different intermolecular forces in the crystals of the three acids.Key words: thermodynamic, calorimetry, differential thermal analysis, phthalic, isophthalic, terephthalic acids, enthalpy of fusion, of sublimation, of formation, of intermolecular bonds, resonance energy, triple point temperature.