The physicochemical properties and viscosity behavior of crown ether 18C6 in the mixture of water with N,N-dimethylformamide

The viscosity of 18-crown-6 (18C6) in the mixtures of N,N-dimethylformamide (DMF) and water (W) is measured within the temperature range of (293.15 to 308.15) K. The values of both dynamic, η, and relative viscosity, ηr, is calculated on the basis of the fluid flow time. The analysis of the viscosity coefficient B of Jones-Dole's equation as well as its derivative relative to temperature (dB/dT) is made. These functions play an important role in showing and discussing the interactions between the mixture component molecules. Moreover, it makes possible to determine their destroying or reinforcing influence on the solvent structure. The effective volume of (18C6 + nH2O) unit is calculated using Breslau-Miller equation and the hydration number of 18C6 supports the existence of hydrophobic hydration of those compounds. The results obtained are discussed in comparison to the results presented in our previous papers. The analysis performed demonstrates the fundamental difference in interactions between the water molecules and hydrophilic urea molecules as well as water molecules and hydrophobic 18C6 molecules. The effect of ring size of cyclic ethers such interactions was also shown.