Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

The standard (p 1/4 0:1 MPa) molar enthalpies of formation of 2,4,6-trichloronitrobenzene, 2,3,5,6-tetrachloronitrobenzene, and pentachloronitrobenzene, in the crystalline state, at T = 298.15 K, were derived from the standard massic energies of combustion, in oxygen, at T = 298.15 K, measured by rotating-bomb combustion calorimetry. The standard molar enthalpies of sublimation, at T = 298.15 K, of 2,4,6-trichloronitrobenzene and pentachloronitrobenzene, were determined from the dependence with the temperature of the vapour pressures, measured by the Knudsen mass-loss effusion method, whereas for 2,3,5,6-tetrachloronitrobenzene, the Calvet drop microcalorimetric technique was used. DcU mocrP/ (kJ mol 1) DfH mocrP/ (kJ mol 1) Dg crH m/ (kJ mol 1) 2,4,6-Trichloronitrobenzene 2663.5 +- 1.1 58.6 +- 1.3 86.7 +- 1.1 2,3,5,6-Tetrachloronitrobenzene 2537.1 +- 1.7 67.0 +- 1.9 91.3 +- 2.5 Pentachloronitrobenzene 2387.4 +- 2.4 98.6 +- 2.5 94.5 +- 0.4 The experimental values are also compared with estimates based on G3(MP2)//B3LYP computations, which have also been extended to all the isomers of the trichloro- and tetrachloronitrobenzene that were not studied experimentally.