The relationships between enthalpy and volume changes of aromatic compounds on melting at Tm and 298.15 K

Abstract

Establishing the relationship between the thermodynamic parameters of melting, on the one hand, and the structural and physicochemical parameters of molecular compounds, on the other, is a long-standing problem. The volume change on melting has been long thought to be related to the entropy of fusion. In this work, we attempted to reveal the connection between the volume change on melting and the thermodynamic parameters of fusion of non-hydrogen-bonded aromatic compounds. Comparative analysis of the fusion enthalpies of different compounds, inherently melting under different conditions, may be ambiguous. Therefore, we additionally employed our recent findings on the experimental determination of the temperature dependence of the fusion enthalpy to adjust the quantities to the same temperature, 298.15 K. Linear correlations were established both at Tm and 298.15 K. An opportunity to use the correlation established at 298.15 K for predicting the fusion and sublimation enthalpies from the crystal density at 298.15 K and the molecular structure, taking advantage of existing approaches for predicting the molar volume of liquids and vaporization enthalpies, was demonstrated. Further investigation of these relationships might help to understand the nature of the melting process.