Hydrogen bonding properties of non-polar solvents

Abstract

A combination of high-throughput NMR titration experiments, UV-Vis absorption titrations and data collected from the literature on 1:1 H-bonded complexes has been used to characterise the H-bond properties of non-polar organic solvents: alkanes, perfluorocarbons, aromatic and halogenated organic solvents. The results are analysed in the context of the electrostatic solvent competition model, which assumes that solvent effects on intermolecular interactions can be interpreted based on the exchange of specific functional group contacts, with minimal involvement of the bulk solvent. For solvents where the H-bond parameters have been measured as solutes in carbon tetrachloride solution, the H-bond parameters measured here for the same compounds as solvents are practically identical, i.e. solute and solvent H-bond parameters are directly interchangable. For the very non-polar solvents, alkanes and perfluorocarbons, the experimental H-bond parameters are significantly larger than expected based on calculated molecular electrostatic potential surfaces. This suggests an increase in the relative importance of van der Waals interactions when electrostatic effects are weak, but there is no detectable difference between the solvation properties of cyclic and linear alkanes, which have different van der Waals interaction properties.