A comparative ultrasonic relaxation study of lower vicinal and terminal alkanediols at 298.15 K in relation to their molecular structure and hydrogen bonding.

Abstract

Ultrasonic relaxation spectra were determined for lower vicinal and terminal alkanediols at ambient pressure and a temperature of 298.15 K. The ultrasound absorption measurements were made by means of the standard pulse technique for 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,4-butanediol, 2,3-butanediol, and 1,5-pentanediol within the frequency range of 5-300 or 10-300 MHz. Relaxation processes were observed for all compounds except 1,2-ethanediol. The relaxation regions were dependent on both the carbon chain length and the position of hydroxyl groups. In addition, the terminal diols showed lower absorption than the adequate vicinal diols did. The results are discussed in terms of molecular structure and molecular interactions, as well as compared with the behavior of adequate lower 1-alkanols. A comparison with classical absorption is also made. The results are discussed in term of shear viscosity relaxation.