Thermodynamic study of 9-anthracenecarboxylic acid

The standard massic energy of combustion, in oxygen, of the crystalline 9-anthracenecarboxylic acid was measured, at T = 298.15 K, by static-bomb combustion calorimetry, from which the standard molar enthalpy of formation, in the condensed phase, was calculated as ΔfHm∘(cr)=-(267.3±3.4)kJ·mol-1. The standard molar enthalpy of sublimation of this acid, at T = 298.15 K, ΔcrgHm∘=(139.4±0.9)kJ·mol-1, was determined from the temperature–vapour pressure dependence, obtained by the Knudsen mass-loss effusion method.From the data presented above, the standard molar enthalpy of formation, in the gaseous phase, at T = 298.15 K, was derived, ΔfHm∘(g)=-(127.9±3.5)kJ·mol-1. The experimental result is interpreted in terms of enthalpic increments, molecular structure and compared with structurally similar compounds.