Experimental thermochemical study of 2,5- and 2,6-dichloro-4-nitroanilines

Abstract

The standard ( p° = 0.1 MPa) molar enthalpies of formation of 2,5- and 2,6-dichloro-4-nitroanilines, in the gaseous phase, at T = 298.15 K, were derived from the combination of the values of the standard molar enthalpies of formation in the crystalline phase, at T = 298.15 K, and the standard molar enthalpies of sublimation, of each compound, at the same temperature. The standard molar enthalpies of formation, in the crystalline phase, at T = 298.15 K, were derived from the standard massic energies of combustion of the two isomers, in oxygen, at T = 298.15 K, measured by rotating-bomb combustion calorimetry. The standard molar enthalpies of sublimation were calculated, by application of the Clausius–Clapeyron equation, to the vapour pressures at several temperatures measured by Knudsen effusion technique. Compound Δ f H m ∘ ( cr ) / ( kJ · mol - 1 ) Δ cr g H m ∘ / ( kJ · mol - 1 ) 2,5-Dichloro-4-nitroaniline −85.6 ± 1.9 114.3 ± 0.9 2,6-Dichloro-4-nitroaniline −107.3 ± 1.4 109.2 ± 0.9 The values of the standard ( p = 0.1 MPa) molar enthalpies of formation of 2,5- and 2,6-dichloro-4-nitroanilines, in the gaseous phase, at T = 298.15 K, were compared with those estimated by the Cox scheme.