Experimental and theoretical thermochemical studies of imidazole, imidazole-2-carboxaldehyde and 2-aminobenzimidazole

Abstract Here were determined the molar standard enthalpies of formation, Δ f H m ° (s), at T  = 298.15 K of imidazole, imidazole-2-carboxaldehyde and 2-aminobenzimidazole from their respective molar standard energies of combustion, obtained by static combustion calorimetry. Enthalpies of sublimation, Δ s g H m ° , at T = 298.15 K were obtained by thermogravimetry measurements. Using data for Δ f H m ° (s) and Δ s g H m ° , the gas phase enthalpies of the two imidazole-derived compounds were calculated. The enthalpy increases due to certain functional groups attached to the imidazole (IM) molecule, and were analyzed that change in the enthalpies using the experimental gas phase enthalpy of formation data. By using theoretical methods, namely G3 and G4, the enthalpies of formation of the compounds under study were obtained and were compared with the experimental ones. In addition, the purity, the melting temperature, the enthalpy of fusion and the heat capacity of the compounds were determined by differential scanning calorimetry.