Ultrasonic relaxation in aqueous solutions of butanediols

Abstract

Ultrasonic absorption and velocity have been measured to investigate the structural and dynamic properties of aqueous solutions of butane-1,4-diol and butane-1,2-diol at 20 °C. In the former solution no excess absorption was found, and in the latter solution a single relaxational process was observed in the frequency range 15–220 MHz. The excess absorption mechanism has been analysed as a solute–solvent interaction, AB ⇌ A + B, and the rate constants for butane-1,2-diol solution have been determined to be k_f= 1.5 × 10⁸ s^–1 and k_b= 1.6 × 10⁸ dm³ mol^–1 s^–1 for the forward and backward steps, respectively. The influence of the position of hydroxy groups in the molecules on the water structure is discussed by a comparison with the results for solutions of the two dihydric alcohol.