Thermodynamics of chlorobenzene, or bromobenzene, or 1-chloronaphthalene or 1,2,4-trichlorobenzene + alkane mixtures

Abstract

The systems C6H5Cl, or C6H5Br, or 1-chloronaphthalene, or 1,2,4-trichlorobenzene, or 1-methylnaphthalene, or 1,2,4-trimethylbenzene + alkane have been investigated by means of the their excess molar properties, including, when the needed data are available, those at constant volume, internal energies (U_Vm^E) and heat capacities (C_Vm^E), and using the DISQUAC, and Flory models, and the concentration-concentration structure factor formalism. The position of the mixtures within the G_m^E (excess molar Gibbs energy) vs. H_m^E (excess molar enthalpy) diagram has been also determined. Interactions between C6H5X molecules become stronger in the sequence X = H ≈ F≈Cl < Br. These interactions are weaker than those between 1-chloronaphtahlene or 1,2,4-trichlorobenzene molecules. It is shown that the considered systems have some common features: dispersive interactions are dominant, structural effects for solutions with shorter n-alkanes are large and U_Vm^Edecreases when the number (n) of C atoms of the alkane increases. This variation is held when an n-alkane is replaced by a branched alkane with the same n in systems with C6H5Cl or 1-chloronaphthalene. This suggests that larger alkanes are poorer breakers of the interactions between aromatic halogenated compounds. Viscosity and C_Vm^E data support this conclusion. The parabolic dependence of C_Vm^E with n indicates that the short orientational order of long n-alkanes is destroyed. Aromaticity and proximity effects are discussed.