KINETIC-STUDY IN AQUEOUS-SOLUTIONS OF ALCOHOLS WITH BUTYL GROUP BY ULTRASONIC METHODS

The ultrasonic absorption coefficients in aqueous solutions of 3-methoxy-1-butanol and 1-methoxy-2-butanol have been measured in the frequency range from 8.5 to 220 MHz at 25-degrees-C. One process associated with a single-relaxational ultrasonic absorption has been found in both solutions. From the concentration dependencies of the relaxation frequency and the amplitude of ultrasonic relaxation, the cause of the relaxation has been attributed to a perturbation of an equilibrium associated with interaction between the solute and the solvent. The rate and thermodynamic parameters have been determined for the reaction and the effect of the isomeric alcohols on water structure has been considered based on these parameters. As results, both alcohols have been found to act as a water structure promoter. The effect of the methoxyl group in the alcohol molecules on the water structure has been speculated to break the water hydrogen bonds, i.e. to act as a structure breaker for water. Also, the results for solutions of other isomers, 2-propoxyethanol and 3-ethoxy-1-propanol, and that of a similar structure, 2-allyloxyethanol, have been compared with those obtained in this study. The effects of substituents in alcohol molecules have been discussed in relation to the water structure. They have also been considered from a comparison with the hydrophobic ability of the alcohols estimated from the concentration dependence of the apparent molar compressibility, along with the result from an ethanol aqueous solution. Both estimations from ultrasonic absorption and compressibility have provided a consistent interpretation for the effects on the water structure. From these present results regarding ultrasonic absorption, it has been speculated that the large ultrasonic absorptions observed near critical points in some alcohol solutions are superimposed with the usual Debye type relaxations.