Dynamic studies of the interaction between diols and water by ultrasonic methods. Part 4.—3-methylbutane-1,3-diol and 2,2-dimethylpropane-1,3-diol solutions

In order to justify the relationship between the structures of diols in aqueous media and their ultrasonic properties, measurements of ultrasonic absorption, sound velocity, density and viscosity have been made in aqueous solutions of 3-methylbutane-1,3-diol and 2,2-dimethylpropane-1,3-diol, which are isomers of each other. In both solutions, a single relaxational ultrasonic absorption has been observed in the frequency range 15–220 MHz. The absorption mechanism has been interpreted in terms of reaction kinetics associated with the interaction between the solute and solvent. As a result, the effect of the solute on the solvent (water) structure has been estimated, and it has been found that these diols act as water-structure promoters. Furthermore, the greater the hydrophobicity of the solute molecule, the more effectively it promotes the water structure. The trend in hydrophobicity determined from sound absorption has been confirmed from the concentration dependences of the compressibility. The correlation between the solvent structural parameters and the compressibility has been examined. The apparent molar volume has also been determined and is discussed with regard to the ultrasonic parameters.