Journal of Chemical and Engineering Data, Vol.54, No.10, 2930-2943, 2009
Hypothetical Thermodynamic Properties. Subcooled Vaporization Enthalpies and Vapor Pressures of Polyaromatic Heterocycles and Related Compounds
The vaporization enthalpies and vapor pressures of the liquid phase from T = 298.15 K to T = 500 K of a series of polyaromatic nitrogen heterocyles (PANH) have been derived using correlation gas chromatography. The vaporization enthalpies at T = 298.15 K measured in kilojoules per mole include: tri-n-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 center dot 1.7H(2)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(-1), T(fus)/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 center dot 1.7H(2)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.