The vaporization enthalpies and liquid vapor pressures of quinoxaline, quinazoline, phthalazine, benzo[c]cinnoline, 1,10-phenanthroline, phenazine, and triphenylamine are measured by correlation gas chromatography and compared to values calculated horn available literature vaporization, sublimation, and fusion enthalpy data Good agreement with the literature is observed for all compounds except the 1,2-diazines and the sublimation enthalpy of triphenylamine The results suggest that liquid 1,2-diazines exhibit an additional intermolecular stabilizing interaction of approximately 6 kJ.mol(-1) not present in other diazine isomers