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

Abstract Relative permittivities at 1 MHz, e r , at 0.1 MPa and (293.15-303.15) K and refractive indices, n D , 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, e r E , are encountered for the methanol system at high alcohol concentrations. The remaining mixtures are characterized by negative e r E values over the whole composition range. At ϕ 1 (volume fraction) = 0.5, e r E changes in the order: methanol > propan-1-ol > butan-1-ol e r E ; (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 e r E measurements for alkan-1-ol + aliphatic amine mixtures; (iv) the aromaticity effect (i.e., the replacement of TEA by pyridine in systems with a given alkan-1-ol) leads to an increase of the mixture polarization. Calculations conducted in the framework of the Kirkwood-Frohlich model are consistent with the previous statements.