Journal of Chemical Thermodynamics, Vol.77, 46-53, 2014
Vapour pressures of 1-methyl derivatives of benzimidazole, pyrazole and indole. The energy of the intermolecular hydrogen bond N-H center dot center dot center dot N
The vapour pressures of the liquid phase of 1-methylpyrazole, 1-methylbenzimidazole and 1-methylindole were measured over the temperature ranges (253.9 to 293.3) K, (303.2 to 372.5) K, and (268.6 to 341.9) K, respectively, using a static method. The vapour pressures of the crystalline phase of the two latter compounds were also measured at temperatures between (301.2 to 328.9) K and (267.6 to 275.5) K, respectively. The results obtained enabled the determination of the standard molar enthalpies and entropies of sublimation and of vaporisation at the mean temperatures of the measurements and at T = 298.15 K. The temperatures and molar enthalpies of fusion were determined using differential scanning calorimetry. The enthalpies of the intermolecular hydrogen bonds N-H center dot center dot center dot N in the crystalline phase of benzimidazole and pyrazole were determined and compared with the result previously determined for the energy of the intermolecular hydrogen bond in crystalline imidazole. (C) 2014 Elsevier Ltd. All rights reserved.
Keywords:Vapour pressures;1-Methylbenzimidazole;1-Methylpyrazole;1-Methylindole;Imidazole;Benzimidazole;Pyrazole;Enthalpy of sublimation;Entropy of sublimation;Enthalpy of vaporisation;Entropy of vaporisation;Temperature of fusion;Enthalpy of fusion;Entropy of fusion;Hydrogen bonds;Supercooled liquid