Dynamical Characterization in Aqueous Solutions of 3-Methoxy- and 3-Ethoxy-1-propanol by Ultrasonic Methods

Article abstract of DOI:10.1246/bcsj.64.1294

3-Methoxy-1-propanol and 3-ethoxy-1-propanol were synthesized through potassium propoxide from 1,3-propanediol.Ultrasonic absorptions in their aqueous solutions were measured in the frequency range from 8.5 to 220 MHz as functions of their concentrations along with the sound velocity and density.In a solution of 3-ethoxy-1-propanol, a single relaxational absorption was observed; the cause was attributed to a perturbation of an equilibrium as AB <-> A + B, where AB represents the solute-solvent complex, A the solute and B the solvent molecules.On the other hand, no relaxational absorption was observed in a 3-methoxy-1-propanol solution up to 4 mol dm^-3.The thermodynamic and the kinetic parameters were evaluated for the abovementioned process from the concentration dependences of the ultrasonic parameters in a 3-ethoxy-1-propanol solution.From evidence concerning the appearance and disappearance of ultrasonic relaxational absorption and comparisons of the rate and thermodynamic constants in aqueous solutions of various alcohols, the alternation of the water structure affected by the addition of the solutes is discussed in connection with the solute structures.The methoxyl group was explicitly found to act as a water structure breaker and the ethoxyl group to do so slightly.