Volumetric, dielectric and transport properties of some liquid tri-n-alkylamines

Abstract

Densities (293.15 ⩽T/K ⩽ 333.15), electric permittivities (293.15 ⩽T/K ⩽ 323.15) and viscosities (293.15 ⩽T/K ⩽ 333.15) of some tertiary n-alkylamines were measured. The values of the density and electric permittivity at 293.15 K and the coefficients of thermal expansion, α, and the temperature dependence of the electric permittivity, γ, are given. The dependence of α(or γ) on the number of carbon atoms in the molecules of the liquids investigated are presented. The Onsager and Kirkwood relations were used to calculate the dipole moments. It was found that within the temperature range studied, the dipole moments are constant and decrease with increasing number of carbon atoms in the alkylamine chains. The values obtained for the Kirkwood correlation coefficient are slightly higher than unity, showing a tendency to increase from triethylamine to tri-n-dodecylamine. To describe the viscosity data, transition-state theory as well as free-volume theory were applied. The values of the energy of activation for viscous flow at constant pressure and the expansion energy of tertiary n-alkylamines were calculated. In addition, triethylamine was classified as a volume-restrained liquid, while the other amines investigated behaved as energy-restrained liquids.