Influence of molecular shape on the melting thermodynamics of non-associated organic compounds

Abstract

The search for the relationship between thermochemical and structural parameters of matter has been a relevant direction of investigations in the field of thermodynamics of organic compounds for many decades. Future research in this direction is essential for the development of fundamental theories and predictive schemes. In this work, we investigated the relationship between the shape of the molecule and the thermodynamic properties of melting for non-associated organic compounds. The sphericity parameter was introduced, and a Python script for its calculation was written for the quantitative characterization of the molecular shape. Analysis of a large amount of literature data revealed a linear correlation between the ratio of fusion enthalpy to molar volume change during melting and the sphericity parameter. The relationships found provide a deeper insight into the melting process. They may serve as a basis for further studies of the influence of molecular structure on its mechanism. In addition, it opens up the possibility of estimating the ratio of the enthalpy of fusion to the molar volume change during melting from the shape of the molecule, which may be useful in predicting melting curve slopes on phase diagrams.