Dielectric relaxation in aqueous solutions of dimethylformamide and dimethylurea

The high-frequency dielectric properties of aqueous solutions of dimethylformamide and dimethyl urea were studied in the range of centimeter wave lengths at 288-308 K. The dielectric relaxation parameters (tau, alpha, Delta G(epsilon)(not equal), Delta H-epsilon(not equal), and Delta S-epsilon(not equal)) of the solutions were determined. Variations of these parameters in series of binary systems containing amide molecules differing in the number of and ratio between polar and nonpolar groups were considered. The presence of stabilizing structural effects in solutions of dimethylformamide and dimethylurea related to hydrophobic hydration of these molecules was demonstrated.