DIELECTRIC-RELAXATION OF NACLO4 SOLUTIONS IN FORMAMIDE, N-METHYLFORMAMIDE, AND N,N-DIMELTHYLFORMAMIDE

Complex permittivity spectra in the frequency range 0.95 less than or equal to nu/[GHz] less than or equal to 89 for N,N-dimethylformamide (DMF), N-methylformamide (NMF), formamide (FA) and their solutions of NaClO4 are investigated to study the change of liquid structure and dynamics arising from the availability of one hydrogen-bond acceptor site together with no (DMF), one (NMF), or two (FA) donor sites on the same molecule. Three solvent relaxation processes are observed for NMF and two for FA and DMF. The relaxation parameters are used to determine salvation numbers. They show that ion-solvent interactions lead to a reduction of the average length of the H-bonded NMF chains but have only moderate influence on the FA structure. An additional solute relaxation process in DMF solutions is due to the diffusion-controlled formation and decomposition of solvent-shared ion pairs.