Descriptors for the hydrogen halides, their solution properties and hydrogen-bonding acidity and basicity: Comparison of the latter with gas phase data

We have used literature data on the solubility of the hydrogen halides in non-aqueous solvents to obtain properties or 'descriptors' of the hydrogen halides, HCl, HBr and HI, that includes their hydrogen-bond acidity and hydrogen-bond basicity. We also use literature data on complexation equilibria in solution to obtain the hydrogen-bond acidity of HF. The descriptors can be used in linear free energy relationships that we have already obtained to predict further values of the solubilities in a very large number of solvents. On our scale of hydrogen bond acidities, A, the hydrogen-bond acidity for HF is very large. HCl has moderate hydrogen-bond acidity, about the same as that of 2,2-dichloroethanol, HBr is a slightly weaker hydrogen-bond acid than ethanol and the hydrogen-bond acidity of HI is so small that HI can be regarded as only a weak to moderate hydrogen-bond acid. The hydrogen-bond basicity of the hydrogen halides is very small indeed. Our hydrogen-bond acidities of the hydrogen halides are consistent with the gas phase electrophilicities previously reported. (C) 2018 Elsevier B.V. All rights reserved.