On dispersion and polar interactions and solvation and cohesion energies. A first round

Abstract

Understanding the role of intermolecular interactions and their specific contributions to thermodynamic quantities remains one of the major goals of Molecular Thermodynamics. Numerous polarity scales and related divisions of intermolecular interactions have been proposed in the literature but the exchange of information between them is not always easy, causing often much confusion. The present work is part of a broader effort for the development of a solid thermodynamic framework for the reliable exchange of such information. The work is a continuation of our recent work on the prediction of the contribution of hydrogen-bonding interactions to solvation enthalpies and free-energies. It focuses on the rest of the contributions arising, primarily, from dispersion and polar interactions. The way these contributions are handled in the relevant literature are discussed. Emphasis is given on the QSPR (Quantitative Structure Property Relationships) - type approaches exemplified by the Linear Solvation Energy Relationship (LSER) approach. The results of two alternative LSER routes to the estimation of solvation enthalpies are critically evaluated and their limitations are discussed. Much emphasis is given on self-solvation, where the relations of solvation energies to cohesion energies, heats of vaporization and internal pressures are examined. Based on this evaluation, an effort is made to establish simple universal methods for the prediction of dispersion and polar contributions to solvation energies free, to a rather significant extent, from the above limitations. These new methods are using molecular descriptors based on quantum – chemical (QC) calculations and referred to as QC-LSER descriptors. The predictions are compared with experimental data and / or other predictive methods in literature. Extensive comparison with the original LSER calculations is made and reported in Supplementary Information file. The strengths, limitations and perspectives of the new approach are also discussed.