Experimental thermochemical study of two chlorodinitroaniline isomers

Abstract

The standard ( p ∘ = 0.1 MPa ) molar enthalpies of formation of 2-chloro-4,6-dinitroaniline and 4-chloro-2,6-dinitroaniline, 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, and of the standard molar enthalpies of sublimation, at the same temperature. The standard molar enthalpies of formation, in the crystalline phase, were derived from the standard massic energies of combustion, in oxygen, measured by rotating-bomb combustion calorimetry. The standard molar enthalpies of sublimation were calculated, by the 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 ) Δ f H m ∘ (g) / ( kJ · mol - 1 ) 2-Chloro-4,6-dinitroaniline 101.0 ± 1.9 115.0 ± 0.9 14.0 ± 2.1 4-Chloro-2,6-dinitroaniline 76.9 ± 1.8 105.2 ± 0.7 28.3 ± 1.9 The values of the standard molar enthalpies of formation of 2-chloro-4,6-dinitroaniline and 4-chloro-2,6-dinitroaniline, in the gaseous phase, at T = 298.15 K, are discussed in terms of enthalpic increments, and the enthalpy of isomerization between the two compounds is compared with the same parameter for two isomers of chloronitroaniline, studied in previous works.