THERMODYNAMIC STUDY OF COUMARIN AND ANTHRONE

The present work is concerned with a thermodynamic study of coumarin and anthrone. The techniques carried out are: combustion calorimetry of small amounts of substance, sublimation calorimetry, differential thermal analysis and heat capacity measurements. The thermodynamic quantities derived are: for coumarin: DELTA-subH(m)-degree (298.15 K) = (83.09 +/- 0.22) kJ mol-1, DELTA-cH(m)-degree (s, 298.15 K) = -(4139.2 +/- 1.7) kJ mol-1, DELTA-fH(m)-degree (s, 298.15 K) = -(259.9 +/- 1.8) kJ mol-1, DELTA-fH(m)-degree (g, 298.15 K) = -(176.8 +/- 1.8) kJ mol-1, DELTA-fusH(m) = (19.14 +/- 0.11) kJ mol-1, T(triple point) = (342.14 +/- 0.01) K for anthrone: DELTA-subH(m)-degree (298.15 K) = (103.32 +/- 0.63) kJ mol-1, DELTA-cH(m)-degree (s, 298.15 K) = -(6858.4 +/- 1.9) kJ mol-1, DELTA-fH(m)-degree (s, 298.15 K) = -(79.9 +/- 2.1) kJ mol-1, DELTA-fH(m)-degree (g, 298.15 K) = (23.4 +/- 2.2) kJ mol-1, DELTA-fusH(m) = 26.8 kJ mol-1, T(triple point) = 429 K. From the experimental results some energy values related to the molecular structure, like resonance energy and atomization enthalpy are determined. They enabled us to realize a comparative study for the two isomers: chromone and coumarin and determine an energy value for some intramolecular chemical bonds in the molecules studied in this paper.