Direct Detection of an Attractive Interaction between Anions and Hydrophobically Hydrated Unpolar Groups

摘要: There exist some indirect hints that in multicomponent aqueous electrolyte solutions anions are attracted to hydrophobically hydrated alkyl groups and it seems this phenomenon is of general nature. In order detect for the first time directly such an attractive interaction we have determined intermolecular dipole-dipole relaxation rates (1/T1)inter protons residing on species dimethylformamide (DMF) dimethylacetamide (DMA), respectively, containing as probe ions either tetraphenylborate (Ph4B−) or tetraphenylarsenate (Ph4As+) ions. We also measured translational diffusion coefficients D DMF, DMA DMF/D2O + phenyl salt (NaPh4B Ph4AsCl) DMA/D2O function concentration. This allowed determination so-called Aij-parameter with respect amide-ion interaction. connected integral over pair correlation results clearly show there a stronger between CH3-groups than cations. simple model explain peculiar attraction by preferentially oriented water molecules at hydrocarbon-water interface.