Thermodynamic study of 9-anthracenecarboxylic acid

Abstract

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 Δ f H m ∘ ( cr ) = - ( 267.3 ± 3.4 ) kJ · mol - 1 . The standard molar enthalpy of sublimation of this acid, at T = 298.15 K, Δ cr g H m ∘ = ( 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, Δ f H m ∘ ( 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.