Thermodynamique de composes azotes. VII. Etude thermochimique du pyrazole et de l'imidazole

Enthalpies of sublimation for pyrazole and imidazole have been obtained by calorimetry at 298.15K. The ΔH⁰_sub (298.15 K) values for these two compounds are, respectively, 69.16 ± 0.32 and 74.50 ± 0.40 kJ mole^?1. From literature data obtained by combustion calorimetry for ΔH⁰_f (c, 298.15 K), the enthalpies of formation of these compounds in the gaseous state (pyrazole: 185.1 ± 2.3 kJ mole^?, imidazole: 133.0 ± 1.7 kJ mole^?1) have been derived. Several energy values related to the molecular structure of these two compounds (as resonance energy, enthalpy of isomerization, …) have been determined. The study of pyrazole has enabled us to contribute to the evaluation of some characteristics of the NN bond.