Hypothetical Thermodynamic Properties. Subcooled Vaporization Enthalpies and Vapor Pressures of Polyaromatic Heterocycles and Related Compounds

The vaporization enthalpies and vapor pressures of the liqiud phase from <i>T</i> = 298.15 K to <i>T</i> = 500 K of a series of polyaromatic nitrogen heterocyles (PANH) have been derived using correlation gas chromatography. The vaporization enthalpies at <i>T</i> = 298.15 K measured in kilojoules per mole include: tri-<i>n</i>-butylamine (62.7 ± 1.3), 2-phenylpyridine (68.4 ± 1.9), 3-phenylpyridine (68.4 ± 1.6), quinazoline (58.9 ± 2.0), (−)-nicotine (63.9 ± 2.1), 4-phenylpyrimidine (68.8 ± 2.5), 2,2-dipyridine (67.0 ± 2.3), 2,4-dipyridine (70.9 ± 1.6), 4,4-dipyridine·1.7H<sub>2</sub>O (70.7 ± 2.4), 4,4-dipyridine (anhydrous, 71.1 ± 2.6), 1,7-phenanthroline (79.4 ± 4.7), 4,7-phenanthroline (80.8 ± 4.8), 2-benzylpyridine (69.8 ± 2.8), and 9-methylcarbazole (79.4 ± 3.2). Fusion enthalpies (kJ·mol<sup>−1</sup>, <i>T</i><sub>fus</sub>/K) are also reported for 2,4-bipyridine (17.4 ± 0.4, 332.8), 4,4-dipyridine (16.1 ± 1.0, 377.5), 4,4-dipyridine·1.7H<sub>2</sub>O (35.5 ± 0.5, 341.3), 4-phenylpyrimidine (18.8 ± 0.3, 334.1), 1,7-phenanthroline (18.2 ± 0.3, 350.3), and 4,7-phenanthroline (21.8 ± 0.5, 445.5). Vaporization enthalpy comparisons are made with available literature values by means of a thermochemical cycle; agreement is within the combined experimental uncertainties for all compounds except 4,4-dipyridine, for which evidence is provided that suggests that the current sublimation enthalpy value in the literature was measured on a hydrated form. Vapor pressures and normal boiling temperatures for the liquid phase are compared with available experimental literature values at elevated temperatures. Good agreement is found for most compounds.