Experimental thermochemical study of the monochloronitrobenzene isomers

Experimental and computational thermochemical study of the dichloronitrobenzene isomers

“…The estimated values of D f H m obtained by the Cox scheme are good estimates for the isomers in which the chlorine atoms are attached into the aromatic ring in meta and para position, as ob- served in a previous study concerned with the thermochemistry of the monochloronitrobenzenes [15]. So, for 3,4-and 3,5-dichloronitrobenzene, the estimations based on the Cox scheme are in very good agreement with the experimental values, cf.…”

“…2,4-and 2,5-dichloronitrobenzene, larger differences, D, are observed. Hence, supported on the former studies devoted to the monochloronitrobenzenes [15] and chloronitroanilines [19], in which it was observed that for benzene derivatives with these two substituents attached in ortho-position a correction term of $22 kJ Á mol À1 should be considered, the estimated values of D f H m ðgÞ for 2,3-, 2,4-, 2,5-, and 2,6-dichloronitrobenzene are, respectively, (45.1 ± 2.3) kJ Á mol À1 , (36.6 ± 2.3) kJ Á mol À1 , (33.4 ± 1.7) kJ Á mol À1 and (44.6 ± 2.3) kJ Á mol À1 , yielding better estimations as compared with the available experimental values.…”

“…the proximity of the halogen atom and the nitro group in the aromatic ring introduces a significant steric destabilization effect, which leads to a slight rotation of the nitro group favouring the non-planar arrangement with a less p delocalization with the aromatic ring. This effect has been also observed for 2-chloronitrobenzene [15] and in the case of the chloronitroaniline isomers [19] in which the chlorine atom and nitro group are attached in the aromatic ring in ortho-positions. Supported by the former cases, it has been observed that, for benzene derivatives with these two substituents attached in ortho-position a correction term of $22 kJ Á mol À1 should be considered in the estimation of D f H m ðgÞ using the Cox scheme.…”

“…Thermodynamic properties of some chloronitrobenzenes have been studied [12][13][14][15]. To the best of our knowledge, however, in what concerns the dichloronitrobenzenes there are only available, experimental results of the vapour pressure, enthalpy of sublimation, and enthalpy of fusion of the 3,4-dichloronitrobenzene, recently reported by Verevkin et al [16].…”

“…The choice of these molecules is due to the fact that the effects of the introduction of chlorine atoms in benzene rings [15,[17][18][19][20][21][22][23] as well as the effect of the same substituents into heterocycles [24][25][26][27][28][29][30] has been, for some years, one of the research objectives of our Research Group on thermochemical properties. The experimental investigation includes the determination of the standard molar energies of combustion, in oxygen, at T = 298.15 K, of four dichloronitrobenzene isomers, using a rotating bomb combustion calorimeter, from which the values of the standard molar enthalpies of formation, in the condensed phase, were derived.…”