Dielectric relaxation of some N,N-disubstituted amides

The dielectric spectrum has been measured between some MHz and 72 GHz for the following 14 pure liquids at 20 degrees C: N,N-Di(methyl-, ethyl-, isopropyl-, butyl-, isobutyl) formamide, 1-formylpiperidine, N-methylformanilide, N,N-di(methyl-, ethyl-, isopropyl) acetamide, N-acetylcaprolactam, N,N-dimethyl-acrylamide, N,N-dimethylpropionamide, and N,N-diethyl-m-toluamide. Moreover, diisobutylformamide and diethyltoluamide have been studied in mixtures with n-hexane over the whole concentration range down to very dilute solutions. The relaxation parameters of all these systems are reported. Particular attention is given to the discussion of the two mixture systems since these exhibit a peculiar concentration dependence of the relaxation strengths of the Debye type spectral components used to describe their spectrum. This behaviour is likely to relate to a flexibility effect which is remarkably intensified on dilution.