Thermodynamic properties of rigid polycyclic molecules. 1: Enthalpies of solution of fused ring polycyclic aromatic hydrocarbons

Enthalpies of solution, ΔsolH, have been measured by using an adiabatic calorimeter, in order to explain thermal stabilization of fused ring polycyclic aromatic hydrocarbon in solution process. Solutes used were benzene, naphthalene, anthracene, phenanthrene, naphthacene and chrysene. Solvents used were cyclohexane, heptane, 1,4-dioxane, benzene and chloroform. The solution process of benzene was endothermic for heptane and cyclohexane, almost athermal for dioxane, and slightly exothermic for chloroform. The ΔsolH results for all other solid solutes were large positive values for all solvents. The results for solid solutes show the good correlation with enthalpy of fusion. Enthalpies of solvation, ΔsolvH, were estimated by subtracting enthalpy of sublimation from ΔsolH. The results show a linear dependence on the number of carbon atoms in solute molecule through near the origin.