Search

Relative permittivities at 1 MHz, , and refractive indices at the sodium D-line, , are reported at 0.1 MPa and at (293.15–303.15) K for the binary systems 1-alkanol + n-hexylamine (HxA). Also, their corresponding excess functions are calculated and correlated. Positive values of the excess permittivities, , are encountered for the methanol system, whereas the remaining mixtures show negative values. This reveals that interactions between unlike molecules contribute positively to . This contribution is dominant for the methanol mixture, while those arising from the breaking of interactions between like molecules are prevalent for the remaining mixtures. At (volume fraction) = 0.5, changes in the order: methanol > 1-propanol > 1-butanol > 1-pentanol < 1-heptanol. Similar variation with the chain length of the 1-alkanol is observed for mixtures such as 1-alkanol + heptane, or + cyclohexylamine, and can be explained in terms of the lower and weaker self-association of longer 1-alkanols. The effect of the replacement of HxA by cyclohexylamine, or by aniline, is also shown. Calculations on molar refractions indicate that dispersive interactions in the systems under study increase with the length of the 1-alkanol. The mixtures are studied by means of the application of the Kirkwood-Fröhlich model, and the Kirkwood correlation factors, including the corresponding excess values, are reported., Ministerio de Educación, Cultura y Deporte for the grants FPU14/04104 and FPU15/05456 respectively. The authors gratefully acknowledge the financial support received from the Consejería de Educación y Cultura of Junta de Castilla y León, under Project BU034U16.

Mixtures involving nitrobenzene and hydrocarbons, or 1-alkanols and 1-nitroalkane, or nitrobenzene have been investigated on the basis of a whole set of thermophysical properties available in the literature. The properties considered are: excess molar functions (enthalpies, entropies, isobaric heat capacities, and volumes), vapour-liquid and liquid-liquid equilibria, permittivities or dynamic viscosities. In addition, the mixtures have been studied by means of the application of the DISQUAC, ERAS, and UNIFAC models, and using the formalism of the concentration-concentration structure factor. The corresponding interaction parameters in the framework of the DISQUAC and ERAS models are reported. In alkane mixtures, dipolar interactions between 1-nitroalkane molecules are weakened when the size of the polar compound increases, accordingly with the relative variation of their effective dipolar moment. Dipolar interactions are stronger in nitrobenzene solutions than in those containing the smaller 1-nitropropane, although both nitroalkanes have very similar effective dipole moment (aromaticity effect). Systems with 1-alkanols are characterized by dipolar interactions between like molecules which sharply increases when the alkanol size increases. Simultaneously, interactions between unlike molecules become weaker, as the OH group is then more sterically hindered. Interactions between unlike molecules are stronger in systems with nitromethane than in nitrobenzene solutions. The replacement of nitromethane by nitroethane in systems with a given 1-alkanol leads to strengthen those effects related with the alcohol self-association. Permittivity data and results on Kirkwood's correlation factors show that the addition of 1-alkanol to a nitroalkane leads to cooperative effects, which increase the dipolar polarization of the solution, in such way that the destruction of the existing structure in pure liquids is partially counterbalanced. This effect is less important when longer 1-alkanols are involved., Consejería de Educacion y Cultura of Junta deCastilla y Leon, under Project BU034U16

The coexistence curves of liquid-liquid equilibrium (LLE) for the mixtures: phenylacetonitrile + heptane, + octane, + nonane, + cyclooctane, or + 2,2,4-trimethylpentane and for 3-phenylpropionitrile + heptane, or + octane are reported. Aromatic nitrile + alkane, + aromatic hydrocarbon or + 1 alkanol systems are investigated using a set of thermophysical properties: phase equilibria (solid-liquid, SLE, vapour-liquid, VLE and LLE), excess molar functions, enthalpies (), isochoric internal energies (), isobaric heat capacities () and volumes (), and the Kirkwood’s correlation factor. Due to proximity effects between the phenyl and the CN groups, dipolar interactions between molecules of aromatic nitriles are stronger than those between molecules of isomeric linear nitriles. Dipolar interactions become weaker in the order: 3-phenylpropionitrile > phenylacetonitrile > benzonitrile. Benzonitrile + aromatic hydrocarbon mixtures are characterized by dispersive interactions and structural effects. The latter are more important in systems with phenylacetonitrile. Structural effects are also present in benzonitrile + n-alkane, or + 1-alkanol + mixtures. The systems mentioned above have been studied using DISQUAC. Interaction parameters for contacts where the CN group in aromatic nitriles participates are given. DISQUAC describes correctly any type of phase equilibria, of benzonitrile + hydrocarbon mixtures and of benzonitrile + cyclohexane, or 1-alkanol systems. Large differences encountered between theoretical values and experimental data for some solutions are discussed. 1-Alkanol + benzonitrile mixtures are also investigated by means of the ERAS model. ERAS represents well of these systems. The curves of solutions with longer 1-alkanols are more poorly described, which has been explained in terms of the existence of structural effects., Consejería de Educación y Cultura of Junta de Castilla y León, under Project BU034U16

Producción Científica, Relative permittivities at 1 MHz and at (293.15-303.15) K are reported for the binary systems N,N-dimethylacetamide (DMA) + N-propylpropan-1-amine (DPA), + N-butylbutan-1-amine (DBA), + butan-1-amine (BA) or + hexan-1-amine (HxA) and for N,N-dimethylformamide (DMF) + aniline. The excess permittivities are large and negative for systems with DMA, whereas they are large and positive for the aniline mixture. From the analysis of these excess permittivity data and of measurements previously reported, it is concluded: (i) the main contribution to the excess permittivity in systems with linear amines arises from the breaking of interactions between like molecules; (ii) in the DMF + aniline mixture, interactions between unlike molecules contribute positively to the excess permittivity, and such a contribution is dominant; (iii) longer linear amines are better breakers of the amide-amide interactions; (iv) interactions between unlike molecules are more easily formed when shorter linear amines, or DMF, participate. These findings are confirmed by a general study conducted in terms of excess values of molar orientational and induced polarizabilities and of the relative Kirkwood correlation factors for systems and components. The ERAS model is also applied to amide + amine mixtures. ERAS represents rather accurately the excess enthalpies and volumes of the mentioned systems. The variation of the cross-association equilibrium constants, determined using ERAS, with the molecular structure is in agreement with that observed for the excess permittivity., The authors gratefully acknowledge the financial support received from the Consejería de Educación y Cultura of Junta de Castilla y León, under Project BU034U16. F. Hevia and A. Cobos are grateful to Ministerio de Educación, Cultura y Deporte for the grants FPU14/04104 and FPU15/05456 respectively.

Interactions and structure of alkanone, or alkanal or dialkyl carbonate + alkane mixtures, or of 2-alkanone + 2-alkanone, or of ketone + dialkyl carbonate systems have been investigated by means of a set of thermodynamic properties and by the application of the Flory model. The properties considered are excess molar quantities: enthalpies, HmE, volumes, VmE, or isobaric heat capacities, CpmE, and liquid-liquid equilibria. Experimental data show that alkane mixtures are characterized by rather strong dipolar interactions. In the case of systems containing ketones with the same number of C atoms and a given alkane, dipolar interactions become weaker in the sequence: aromatic > cyclic > linear. In addition, the mentioned interactions become also weaker in the order: dialkyl carbonate > linear alkanone > linear alkanal. This is an important result, as carbonates show lower effective dipole moments than the other compounds, and it suggests that the group size may be relevant when evaluating thermodynamic properties of liquid mixtures. Results on HmE from the Flory model show that orientational effects (i.e., non-random mixing) are rather similar for systems with linear, cyclic or aromatic ketones or alkanals and alkanes. In contrast, orientational effects become weaker in dialkyl carbonate + alkane mixtures. The behavior of 2-alkanone + 2-alkanone systems and of mixtures of longer 2-alkanones or cyclohexanone with dialkyl carbonate is close to random mixing. Larger orientational effects are encountered in solutions of carbonates and shorter 2-alkanones., Consejería de Educación y Cultura of Junta de Castilla y León, under Project BU034U16.