Thermodynamics of mixtures with strongly negative deviations from Raoult’s law. XVII. Permittivities and refractive indices for alkan-1-ol + N,N-diethylethanamine systems at (293.15–303.15) K. Application of the Kirkwood-Fröhlich model

Publication date: February 2020Source: The Journal of Chemical Thermodynamics, Volume 141Author(s): Fernando Hevia, Juan Antonio González, Ana Cobos, Isaías García de la Fuente, L.F. SanzAbstractRelative permittivities at 1 MHz, εr, at 0.1 MPa and (293.15–303.15) K and refractive indices, nD, at similar conditions have been measured for the alkan-1-ol (methanol, propan-1-ol, butan-1-ol, pentan-1-ol or heptan-1-ol) + N,N-diethylethanamine (TEA) systems. Positive values of the excess permittivities, εrE, are encountered for the methanol system at high alcohol concentrations. The remaining mixtures are characterized by negative εrE values over the whole composition range. At ϕ1 (volume fraction) = 0.5, εrE changes in the order: methanol > propan-1-ol > butan-1-ol < pentan-1-ol < heptan-1-ol. Mixtures formed by alkan-1-ol and an isomeric amine, hexan-1-amine (HxA) or N-propylpropan-1-amine (DPA) or cyclohexylamine, behave similarly. This has been explained in terms of the lower and weaker self-association of longer alkan-1-ols. From the permittivity data, it is shown that: (i) (alkan-1-ol)-TEA interactions contribute positively to εrE; (ii) TEA is an effective breaker of the network of the alkan-1-ols; (iii) structural effects, which are very important for the volumetric and calorimetric data of alkan-1-ol + TEA systems, are also relevant when evaluating dielectric data. This is confirmed by the comparison of εrE measurements ...
Source: The Journal of Chemical Thermodynamics - Category: Chemistry Source Type: research