Intermolecular association and dielectric relaxation in some liquid amides

The equilibrium dielectric constants of three isomeric N-methylvaleramides are reported over a wide range of temperature. Analysis of the data in terms of Kirkwood's correlation factor suggests that the liquids are extensively associated into linear chains and that the extent of association is essentially independent of the size and shape of the alkyl group. Dielectric dispersion was measured (0.5-200 MHz) for these compounds as well as the isomeric N-butylacetamides and also N-ethylacetamide. The dispersion loci all follow the Debye equation and the relaxation times show a specific dependence on the size and shape of the alkyl group, but not on whether it is in the acid or the amine position. Activation energies for relaxation, viscous flow, and conduction are compared and the nature of liquid N-mono-substituted amides is discussed.