Abstract: Interaction of ion-solvent and ion-ion in N,N-dimethylformamide solution of NaClO₄ and NaNO₃ were investigated using IR spectroscopy. The characteristic absorption band intensities of C—N band and CO band were contrasted on amide group by the increasing of sodium ion concentration. The ν₂ band of NaNO₃ and the ν₁ band of NaClO₄ indicated the law of ion association. To compared with N—C—N vibration peak(865 cm^-1), based on the deconvolution and quantitative calculation on obtained spectra, solvation numbers 1—4 of Na⁺ is calculated. Moreover the optimization and thermodynamic properties calculated by quantum chemistry obtained optimized structures consistenting with experiment. It had been found that the band of amide group obviously changed. Ion solvation possibly led to a new conjugated bond in the interior of amide group. We discussed the ion association of solution to explain the change of the structure by dimethylformamide.

Key words: N,N-Dimethylformamide, Ion solvation, Ion association