Variations in the concentration of microwave dielectric spectra in a water-acetonitrile system

Abstract

Relaxation models for describing the microwave dielectric spectra of acetonitrile (AN) solutions are presented. It is noted that the models, which contain two fundamental Debye spectral components, can be used for most concentrations. The separate influence of polar and nonpolar molecules in groups of AN molecules on the initial structure of water in the solution is established and found to have different signs. A schematic of the concentration’s structural transition from water to pure AN is given. It is concluded that integrated clusters consisting of water and AN molecules are found in the system’s region of medium concentrations (0.4–0.6 m.f. AN), where the motions of water molecules are slowed down and it is stabilized due to the hydrophobic hydration of nonpolar AN groups. It is shown that the AN molecules are more tightly bound compared than pure AN due to the formation of AN-H2O bonds over the range of concentrations.