Dielectric Properties of Alkanediol/Water Mixtures

Abstract

At 25 °C the complex dielectric permittivity has been measured as a function of frequency ν (1 MHz ≤ ν ≤ 56 GHz) and mole fraction x (0 ≤ x ≤ 1) for mixtures of water with 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,7-heptanediol. Some parameters like the (extrapolated) static permittivity and the characteristic relaxation time can be directly taken from the spectra. But the spectra can be also analytically represented by semiempirical relaxation spectral functions. A function containing two relaxation terms, a high-frequency Cole−Cole term and a Debye term with smaller relaxation frequency, appears to be appropriate. The relaxation parameters of the water/diol mixtures have been evaluated and compared to other water/organic solvent systems to show that (i) a high degree of permanent electric dipole orientation correlation exists in the diols that is significantly reduced on addition of water, (ii) the characteristic relaxation time reflects a substantial effect of entropy in the mechanism of dielectric relaxation but exhibits also a significant difference from monohydric alcohol/water systems, and (iii) the subdivision of the spectra into two relaxation terms seems to be due to regions of different concentration of hydrogen-bonding sites within the mixtures.

The dielectric relaxation of binary mixtures of propanediamine and propanediol

“…Sudo et al determined the dielectric relaxation time for various alcohols and water mixtures [7]. The relaxation time of alcohol-water system increases monotonically with increasing alcohol concentration [7,8].…”

Measurement and correlation of excess molar enthalpy for (1,2-propanediol, or 1,3-propanediol, or 1,4-butanediol+water) at the temperatures (298.15, 323.15, and 343.15) K

“…The size and shape of apolar groups play a major role on the hydrophobic hydration for alcohols, as observed by Okazaki et al [4] and Nakanishi et al [5] using a Monte Carlo simulation. Alkanediols are chemically very similar to alcohols and the hydration properties have been observed for these compounds by several authors [6][7][8][9]. The presence of an additional hydroxyl group in the molecule turns the position of the two hydroxyl groups very important for the hydrophobic hydration as observed by Takahashi and Nishi [6] and Jerie et al [7].…”

Structural and interactional studies of homologous series of α,ω-alkanediols in N,N-dimethylformamide

“…Alkanediols are the simplest model structural units for polyhydroxy compounds. Alkanediols are chemically very similar to alcohols and the hydration properties have been observed for these compounds by several authors [2,3,[7][8][9][10][11]. The presence of the additional hydroxyl group in the diol molecule makes the position of the twohydroxyl groups very important for the hydrophobic hydration.…”