Intermolecular forces between molecules of different species

University of California, Berkeley, U.S.A..

Abstract

The assumption that the intermolecular attractive potentials between molecules of different species are adequately represented by a geometric mean of those between like species serves well to account for solubility relations for mixtures of molecules of similar electronic types but not for others. It agrees well for solubilities of iodine in 15 solvents covering a 300-fold range, but fails badly for solubilities newly determined of CF₄ and SF₆. It seems desirable to recognize differences in the nature of molecular force fields between molecules of different types: hydrogen and paraffins, with bonding electrons only; aromatics and olefins with pi-electrons; halogens and halides with non-bonding outer electrons, fluorocarbons, and species capable of electron donor-acceptor interaction. There is need for a theory of intermolecular potentials far more sophisticated than the primitive London theory and 6-12 central, radial potentials.