Hydrogen bonding and van der Waals forces contributions to the melting enthalpy: insights from volumetric and spectroscopic data

The investigation of the hydrogen bonding influence on the thermodynamic properties of matter is of great importance for both fundamental and applied science. In this work, we analyzed the relationship between the fusion enthalpies and volume changes on melting for associated molecular substances. The relationship between the enthalpy-to-volume ratio and the molecular sphericity parameter previously found for non-hydrogen-bonded systems enabled the division of the fusion enthalpy into van der Waals and specific interactions contributions. On the other hand, hydrogen bonding strength change on melting was evaluated based on the Badger-Bauer rule. These two independent estimates of the hydrogen bonding effect on the fusion enthalpies agreed within 1.1 kJ mol^-1 on average for a diverse set of alcohols, phenols, carboxylic acids, and water. Thus, an approach for studying a complicated balance between hydrogen bonding and van der Waals forces contributions into the fusion enthalpy of non-electrolytes, combining the spectroscopic, calorimetric, and volumetric data, accounting for their molecular structure, was developed for the first time.