Enthalpies of solution, partial molar volumes and isentropic compressibilities of polycyclic aromatic hydrocarbons in 1-methyl-2-pyrrolidone at 298.15 K

In order to explain the solvation behavior of polycyclic aromatic hydrocarbons in polar solvents, the enthalpies of salvation, ΔsolvH  , the partial molar volumes at infinite dilution, Vm,1∞, and the partial molar isentropic compression at infinite dilution, Ks,m,1∞, have been determined for some polycyclic aromatic hydrocarbons in 1-methyl-2-pyrrolidone (NMP) from measurements of enthalpies of solution, ΔsolnH, densities and sound velocities. UV-spectra have also been obtained to evaluate the intermolecular interactions. Aromatic hydrocarbons investigated were benzene, naphthalene, anthracene, phenanthrene, chrysene, biphenyl and o-, m-, p-terphenyl. The enthalpy ΔsolnH is endothermic for each aromatics, except for benzene, for which it is exothermic. The values of ΔsolvH  , Vm,1∞, and Ks,m,1∞ depend linearly on the number of carbon atoms in the aromatic molecules, except for those of o- and p-isomers of terphenyl supporting then that the group contribution principle applies for most of the investigated components. Compared with previous works the absolute values of ΔsolvH   in polar solvent are relatively larger than those in a non-polar solvent. On the other hand, the values of Vm,1∞ in the polar solvents are smaller than those in the non-polar solvent. These results can be attributed to the formation of intermolecular interactions in mixture, like dipole–induced dipole intermolecular interactions between the polycyclic aromatic hydrocarbon and NMP. A shift to the long wavelength was observed in the peak of UV spectra of benzene and naphthalene in the polar solvents. It suggests the existence of an induced effect in the intermolecular interactions.