Experimental and computational thermochemical study of the dichloronitrobenzene isomers

Abstract

The standard ( p° = 0.1 MPa) molar enthalpies of formation of 2,4-, 2,5-, 3,4- and 3,5-dichloronitrobenzene isomers, in the crystalline state, at T = 298.15 K, were derived from the standard ( p° = 0.1 MPa) massic energies of combustion, in oxygen, at T = 298.15 K, measured by rotating bomb combustion calorimetry. The standard molar enthalpies of sublimation of the four isomers, at T = 298.15 K, were obtained by high-temperature Calvet microcalorimetry. - Δ c U m ∘ ( cr ) / ( kJ · mol - 1 ) - Δ f H m ∘ (cr) / ( kJ · mol - 1 ) Δ cr g H m ∘ / ( kJ · mol - 1 ) 2,4-Dichloronitrobenzene 2792.8 ± 0.9 47.4 ± 1.2 87.8 ± 1.7 2,5-Dichloronitrobenzene 2793.0 ± 1.8 47.2 ± 2.0 87.4 ± 2.5 3,4-Dichloronitrobenzene 2774.1 ± 1.2 66.1 ± 1.4 85.8 ± 2.5 3,5-Dichloronitrobenzene 2769.6 ± 0.9 70.6 ± 1.2 83.2 ± 1.5 From the determined experimental results, the values of the gaseous standard ( p° = 0.1 MPa) molar enthalpies of formation were derived. The gas-phase enthalpies of formation of all the six chloronitrobenzene isomers were also estimated by the Cox scheme and by computational thermochemistry methods and compared with the available experimental values.