arXiv subjects

Fernando Hevia

Publications and source records attributed to Fernando Hevia.

At least 37 records · Page 2Linked to original sources

arXiv2024

Thermodynamics of mixtures containing aromatic nitriles

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 ($H_{\text{m}}^{\text{E}}$), isochoric internal energies, isobaric heat capacities ($C_{p \text{m}}^{\text{E}}$) and volumes ($V_{\text{m}}^{\text{E}}$), and the Kirkwood 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 and DISQUAC results on excess properties and phase equilibria are discussed. 1-Alkanol + benzonitrile mixtures are also investigated by means of the ERAS model. ERAS represents well $H_{\text{m}}^{\text{E}}$ of these systems. The $V_{\text{m}}^{\text{E}}$ curves of solutions with longer 1-alkanols are more poorly described, which has been explained in terms of the existence of structural effects.

physics.chem-ph↗

arXiv2024

Thermodynamics of amide+amine mixtures. 4. Relative permittivities of N,N-dimethylacetamide+N-propylpropan-1-amine, +N-butylbutan-1-amine, +butan-1-amine, or +hexan-1-amine and of N,N-dimethylformamide+aniline mixtures

Relative permittivities at 1 MHz, $\varepsilon_{\text{r}}$, 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, $\varepsilon_{\text{r}}^{\text{E}}$, are large and negative for systems with DMA, whereas they are large and positive for the aniline mixture. From the analysis of these $\varepsilon_{\text{r}}^{\text{E}}$ data and of measurements previously reported, it is concluded: (i) the main contribution to $\varepsilon_{\text{r}}^{\text{E}}$ 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 $\varepsilon_{\text{r}}^{\text{E}}$, 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 $\varepsilon_{\text{r}}^{\text{E}}$.

physics.chem-ph↗

arXiv2024

Liquid-liquid equilibria for (2-hydroxy benzaldehyde + n-alkane) mixtures. Intermolecular and proximity effects in systems containing hydroxyl and aldehyde groups

The liquid-liquid equilibrium (LLE) curves have been determined for the 2-hydroxyl-benzaldehyde (salicylaldehyde, SAC) + CH$_3$(CH$_2$)$_n$CH$_3$ mixtures ($n$ = 5,6,7,8,9). The equilibrium temperatures were determined observing, by means of a laser scattering technique, the turbidity produced on cooling when a second phase takes place. All the systems show an upper critical solution temperature, which linearly increases with $n$. Intermolecular effects have been investigated in alkanol + benzaldehyde systems using data from the literature. Interactions in 1-alkanol mixtures are mainly of dipolar type. The corresponding excess molar enthalpies, $H_{\text{m}}^{\text{E}}$, are large and positive, which reveals that interactions between like molecules are dominant. Interactions between unlike molecules are stronger for the methanol-containing system. For the other mixtures, the enthalpy of the (1-alkanol)-benzaldehyde interactions remains more or less constant. At 298.15 K and equimolar composition, the replacement of a linear polar solvent by the isomeric aromatic one leads to increased $H_{\text{m}}^{\text{E}}$ values in systems with a given 1-alkanol. The phenol + benzaldehyde system shows strongly negative deviations from the Raoult's law. Proximity effects have been examined in SAC + hydrocarbon mixtures. Alkane-containing systems are essentially characterized by dipolar interactions, while dispersive interactions are prevalent in the solution with benzene. All the mixtures have been treated in terms of DISQUAC. The interaction parameters for the OH/CHO contacts and for the SAC/aromatic and SAC/alkane contacts have been reported. DISQUAC provides a correct description of the thermodynamic properties considered. In the case of SAC systems, this is done by defining a new specific group HO-C-C-CHO for salicylaldehyde.

physics.chem-ph↗

arXiv2024

Orientational effects in mixtures of organic carbonates with alkanes or 1-alkanols

Interactions and structure of organic carbonate + alkane, and 1-alkanol + organic carbonate mixtures have been investigated by means of a set of molar excess functions: enthalpies, volumes, isobaric heat capacities, or entropies; and considering internal pressure, liquid-liquid equilibria or permittivity data. In addition, the mentioned systems have been studied using the Flory model and the concentration-concentration structure factor formalism. The mixtures under consideration are characterized by dipolar interactions and by homocoordination (that is, by interactions between like molecules). In systems with a given solvent, dipolar interactions are weakened in the order: propylene carbonate (PC) > dimethyl carbonate (DMC) > diethyl carbonate (DEC). Comparison of mixtures containing DMC or DEC with those involving 2-propanone or 3-pentanone shows that dipolar interactions are not determined merely by values of the dipole moment, but they also depend on the group size. The enthalpies of the alkanol-carbonate interactions have been evaluated from calorimetric data. They are stronger in DMC solutions and become weaker when the alcohol size increases in mixtures with a given carbonate. Application of the Flory model to 43 systems of the type 1-alkanol + carbonate provides a mean relative standard deviation for excess molar enthalpy equal to 0.107. Results reveal that orientational effects decrease in the order DEC > PC > DMC. Orientational effects are particularly relevant in methanol or ethanol + DEC mixtures. Interestingly, the mentioned effects are weaker in 1-alkanol + DMC mixtures than in DMC + alkane systems. A similar trend is observed in DEC solutions when the considered alcohol is longer than ethanol.

physics.chem-ph↗

arXiv2024

Dissolution of sulfur dioxide and nitrogen monoxide in water

Sulfur dioxide (SO$_2$) and nitrogen monoxide (NO) are some of the gas impurities present in the carbon dioxide (CO$_2$) separated from fume using post combustion capture process. Even in a small amount, these impurities may have an impact on storage process development. The dissolution of such gases in aqueous phase is part of the studies carried out to develop processes and analyze the risks in case of geological storage. The enthalpies of solution of SO$_2$ and NO in water were here investigated by calorimetry, using a flow calorimetric technique. The enthalpies of solution were determined at 323.15 K and 373.15 K for sulfur dioxide, and at 323.15 K for nitrogen monoxide. The experimental enthalpy data were used together with available solubility data to test thermodynamic models representative of vapor-liquid equilibrium.

physics.chem-ph↗

arXiv2024

Thermodynamics of amide + amine mixtures. 3. Relative permittivities of N,N-dimethylformamide + N-propylpropan-1-amine, + N-butylbutan-1-amine, + butan-1-amine, or + hexan-1-amine systems at several temperatures

Relative permittivities at 1 MHz, $\varepsilon_{\text{r}}$, and at (293.15-303.15) K, are reported for the binary systems N,N-dimethylformamide (DMF) + N-propylpropan-1-amine (DPA), + N-butylbutan-1-amine (DBA), + butan-1-amine (BA) or + hexan-1-amine (HxA). The values of the excess relative permittivities, $\varepsilon_{\text{r}}^{\text{E}}$, have also been determined for these solutions. The measurements were realized by means of a precision impedance analyser 4294A, to which a 16452A cell connected using a 16048G test lead, all of them from Agilent. The $\varepsilon_{\text{r}}^{\text{E}}$ values are large and negative, and diminish when the size of the amine increases along a homologous series, which has been ascribed mainly to the rupture of interactions between like molecules along mixing. Calculations on excess molar orientational polarizabilities support this conclusion, indicating a dominant contribution to $\varepsilon_{\text{r}}^{\text{E}}$ from the orientational polarizability of the molecules in the mixture. The analysis of excess relative Kirkwood correlation factors shows that the correlation between dipoles is effectively decreased along the mixing process.

physics.chem-ph↗

arXiv2024

Thermodynamics of chlorobenzene, or bromobenzene, or 1-chloronaphthalene or 1,2,4-trichlorobenzene + alkane mixtures

The systems C$_6$H$_5$Cl, or C$_6$H$_5$Br, or 1-chloronaphthalene, or 1,2,4-trichlorobenzene, or 1-methylnaphthalene, or 1,2,4-trimethylbenzene + alkane have been investigated by means of the their excess molar properties, including, when the needed data are available, those at constant volume, internal energies ($U_{V\text{m}}^{\text{E}}$) and heat capacities ($C_{V\text{m}}^{\text{E}}$), and using the DISQUAC, and Flory models, and the concentration-concentration structure factor formalism. The position of the mixtures within the $G_{\text{m}}^{\text{E}}$ (excess molar Gibbs energy) vs. $H_{\text{m}}^{\text{E}}$ (excess molar enthalpy) diagram has been also determined. Interactions between C$_6$H$_5$X molecules become stronger in the sequence X = H $\approx$ F $\approx$ Cl < Br. These interactions are weaker than those between 1-chloronaphtahlene or 1,2,4-trichlorobenzene molecules. It is shown that the considered systems have some common features: dispersive interactions are dominant, structural effects for solutions with shorter n-alkanes are large and $U_{V\text{m}}^{\text{E}}$ decreases when the number ($n$) of C atoms of the alkane increases. This variation is held when an n-alkane is replaced by a branched alkane with the same $n$ in systems with C$_6$H$_5$Cl or 1-chloronaphthalene. This suggests that larger alkanes are poorer breakers of the interactions between aromatic halogenated compounds. Viscosity and $C_{V\text{m}}^{\text{E}}$ data support this conclusion. The parabolic dependence of $C_{V\text{m}}^{\text{E}}$ with $n$ indicates that the short orientational order of long n-alkanes is destroyed. Aromaticity and proximity effects are discussed.

physics.chem-ph↗

arXiv2024

Thermodynamics of mixtures containing a fluorinated benzene and a hydrocarbon

Fluorobenzene, or 1,4-difluorobenzene or hexafluorobenzene + alkane mixtures and hexafluorobenzene + benzene, or + toluene, or + 1,4-dimethylbenzene systems have been studied using thermodynamic properties from the literature and through the application of the DISQUAC and UNIFAC (Dortmund) models and the concentration-concentration structure factor ($S_{\text{CC}}(0)$). Interaction parameters for the contacts F/alkane and F/aromatic have been determined for DISQUAC, and they have been taken from the literature for UNIFAC. Both models predict double azeotropy for the C$_6$F$_6$ + C$_6$H$_6$ system, although in different temperature ranges. Excess molar enthalpies ($H_{\text{m}}^{\text{E}}$) of the fluorobenzene, or 1,4-difluorobenzene + n-alkane systems are positive and are accurately described by the models using interaction parameters independent of the n-alkane, discarding Patterson's effect in such mixtures. DISQUAC calculations confirm that conclusion for C$_6$F$_6$ + n-alkane mixtures. DISQUAC provides better results than UNIFAC on excess molar isobaric heat capacities ($C_{p\text{m}}^{\text{E}}$) of solutions involving n-alkanes, or on $H_{\text{m}}^{\text{E}}$ of C$_6$F$_6$ + aromatic hydrocarbon systems. For mixtures with a given n-alkane, the relative variation of excess molar internal energies at constant volume ($U_{V\text{m}}^{\text{E}}$) and $H_{\text{m}}^{\text{E}}$ and with the fluorohydrocarbons is different, due to structural effects. C$_6$F$_6$ + aromatic hydrocarbon mixtures are characterized by interactions between unlike molecules, as seen from their negative $H_{\text{m}}^{\text{E}}$ values. The $S_{\text{CC}}(0)$ formalism reveals that homocoordination is more important in C$_6$F$_6$ + n-alkane mixtures than in the corresponding systems with C$_6$H$_5$F, and that heterocoordination is dominant in the solutions of C$_6$F$_6$ with an aromatic hydrocarbon.

physics.chem-ph↗

arXiv2024

Thermodynamics of mixtures with strongly negative deviations from Raoult's law. XV. Permittivities and refractive indices for 1-alkanol + n-hexylamine systems at (293.15-303.15) K. Application of the Kirkwood-Fröhlich model

Relative permittivities at 1 MHz, $\varepsilon_{\text{r}}$, and refractive indices at the sodium D-line, $n_{\text{D}}$, 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, $\varepsilon_{\text{r}}^{\text{E}}$, are encountered for the methanol system, whereas the remaining mixtures show negative values. This reveals that interactions between unlike molecules contribute positively to $\varepsilon_{\text{r}}^{\text{E}}$. 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 $ϕ_1$ (volume fraction) = 0.5, $\varepsilon_{\text{r}}^{\text{E}}$ 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.

physics.chem-ph↗

arXiv2024

Thermodynamics of amide+ketone mixtures. 2. Volumetric, speed of sound and refractive index data for N,N-dimethylacetamide+2-alkanone systems at several temperatures. Application of Flory's model to tertiary amide+n-alkanone systems

Data on density, $ρ$, speed of sound, $c$, and refractive index, $n_{\text{D}}$, have been reported at (293-303.15) K for the N,N-dimethylacetamide (DMA) + CH$_3$CO(CH$_2$)$_{u-1}$CH$_3$ ($u$ = 1, 2, 3) systems, and at 298.15 K for the mixture with $u$ = 5. These data have been used to compute excess molar volumes, $V_{\text{m}}^{\text{E}}$, excess adiabatic compressibilities, $κ_S^{\text{E}}$, and excess speeds of sound $c^{\text{E}}$. Negative $V_{\text{m}}^{\text{E}}$ values indicate the existence of structural effects and interactions between unlike molecules. From excess molar enthalpies, $H_{\text{m}}^{\text{E}}$, available in the literature for N,N-dimethylformamide (DMF), or N-methylpyrrolidone (NMP) + n-alkanone systems, it is shown: (i) amide-ketone interactions are stronger in DMF systems than in those with NMP; (ii) they become weaker when $u$ increases in mixtures with a given amide. Structural effects largely contribute to $H_{\text{m}}^{\text{E}}$ and are more relevant in mixtures containing NMP. The application of the Flory's model reveals that the random mixing hypothesis is valid to a large extent for DMF solutions, while NMP systems are characterized by rather strong orientational effects. From values of molar refraction and of the product $P_{\text{int}} V_{\text{m}}$ (where $P_{\text{int}}$ is the internal pressure and $V_{\text{m}}$ the molar volume), it is concluded that dispersive interactions increase with $u$, or when DMF is replaced by DMA in mixtures with a fixed ketone.

physics.chem-ph↗

arXiv2024

Orientational effects in alkanone, alkanal or dialkyl carbonate + alkane mixtures and in alkanone + alkanone or + dialkyl carbonate systems

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, $H_{\text{m}}^{\text{E}}$, volumes, $V_{\text{m}}^{\text{E}}$, or isobaric heat capacities, $C_{p \text{m}}^{\text{E}}$, 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 $H_{\text{m}}^{\text{E}}$ 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 behaviour 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.

physics.chem-ph↗

arXiv2024

Orientational and steric effects in linear alkanoates + N-Alkane mixtures

The CH$_3$(CH$_2$)$_u$COO(CH$_3$)$_v$CH$_3$ + n-alkane mixtures have been investigated on the basis of an experimental database containing effective dipole moments of esters, and excess molar functions of the systems: enthalpies ($H_{\text{m}}^{\text{E}}$), volumes ($V_{\text{m}}^{\text{E}}$), isobaric heat capacities ($C_{p\text{m}}^{\text{E}}$) and isochoric internal energies ($U_{V\text{m}}^{\text{E}}$) and by means of the application of the Flory model and the Kirkwood-Buff formalism. The situation of the mixtures within the $G_{\text{m}}^{\text{E}}$ (excess molar Gibbs energy) vs. $H_{\text{m}}^{\text{E}}$ diagram has also been briefly considered. Results indicate that dispersive interactions are dominant and that steric effects can explain some differences between solutions containing heptane and isomeric esters. Proximity and orientational effects are also discussed in diester + hexane mixtures. In the case of systems with a given alkane and different isomeric polar compounds, orientational effects become weaker in the order: n-alkanone > dialkyl carbonate > n-alkanoate. Results from the Kirkwood-Buff formalism indicate that the number of ester-ester interactions decreases in systems with alkyl ethanoates when the alkyl size increases and that preferential solvation between polar molecules decreases as follows: dialkyl carbonate > n-alkanone > n-alkanoate.

physics.chem-ph↗

arXiv2024

Density and speed of sound of (iodobenzene + n-alkane) liquid mixtures at $T$ = (288.15 to 308.15) K. Application of the Prigogine-Flory-Patterson model

(Iodobenzene + n-alkane) liquid mixtures have been studied experimentally, in terms of densities and speeds of sound at a pressure $p$ = 0.1 MPa and in the temperature range $T$ = (288.15 to 308.15) K, and theoretically, by the application of the Prigogine-Flory-Patterson (PFP) model. The n-alkanes considered are n-heptane, n-decane, n-dodecane, and n-tetradecane. Excess molar volumes ($V_{\text{m}}^{\text{E}}$) and excess isentropic compressibilities ($κ_S^{\text{E}}$) have been calculated and correlated by Redlich-Kister polynomials. ${(\partial{V_{\text{m}}^{\text{E}}}/\partial T)}_p$ curves at the same (p,T) conditions have been obtained from correlated $V_{\text{m}}^{\text{E}}$ values. From these experimental results and the knowledge of the excess molar enthalpies and volumes of mixtures containing fluorobenzene, chlorobenzene or bromobenzene with n-alkanes, we have inferred: (i) the presence of structural effects, especially important for the n-heptane mixture and less relevant for volumetric properties as the length of the n-alkane increases; and (ii) that the interactional effects on $V_{\text{m}}^{\text{E}}$ do not vary appreciably with the length of the n-alkane, so the observed $V_{\text{m}}^{\text{E}}$ variation is fundamentally determined by the corresponding variation of the contribution from structural effects. The application of the PFP model supports this interpretation, providing free volume contributions to $V_{\text{m}}^{\text{E}}$ that vary parallelly to $V_{\text{m}}^{\text{E}}$ with the length of the n-alkane, and interactional contributions that rest approximately constant independently of the n-alkane size.

physics.chem-ph↗

arXiv2024

Thermodynamics of 2-alkanol + polar organic solvent mixtures. I. Systems with ketones, ethers or organic carbonates

The mixtures 2-propanol or 2-butanol + n-alkanone, or + acetophenone or + linear monoether, or + cyclic ether, or + linear organic carbonate, or + propylene carbonate have been investigated using thermodynamic data, and in terms of the Flory theory, and the Kirkwood-Buff integrals. The data considered are: excess molar enthalpies ($H_{\text{m}}^{\text{E}}$), volumes, entropies, and the temperature dependence of $H_{\text{m}}^{\text{E}}$. The enthalpy of the 2-alkanol-solvent interactions have been determined, and the different contributions to $H_{\text{m}}^{\text{E}}$ are discussed. It is shown that $H_{\text{m}}^{\text{E}}$ values of the 2-alkanol (fixed) + n-alkanone, or + linear carbonate mixtures change in the same manner that for n-alkanone, or linear carbonate + n-alkane (fixed) systems. In contrast, $H_{\text{m}}^{\text{E}}$ values of 2-alkanol (fixed) + linear monoether or + n-alkane mixtures change similarly. This set of results suggests that solvent-solvent interactions are determinant in systems with n-alkanone or linear carbonate, while interactions between alcohol molecules are determinant in mixtures with linear monoethers. According to the Flory model, orientational effects in systems with a given 2-alkanol become weaker in the sequence: linear monoether > linear organic carbonate > n-alkanone, and are stronger in solutions with a cyclic monoether than in those with cyclic diethers, and in systems with acetophenone or propylene carbonate than in the mixtures with the corresponding linear solvents. Results obtained from the Kirkwood-Buff integrals are consistent with these findings. The application of Flory model reveals that orientational effects are similar in systems with 1- or 2-alkanols, with the exception of solutions with linear monoethers, where such effects are stronger in mixtures containing 1-alkanols.

physics.chem-ph↗

arXiv2024

Viscosities of iodobenzene + n-alkane mixtures at (288.15-308.15) K. Measurements and results from models

Kinematic viscosities were measured for iodobenzene + n-alkane mixtures at (288.15-308.15) K and atmospheric pressure. Using our previous density data, dynamic viscosities ($η$), deviations in absolute viscosity ($Δη$) and quantities of viscous flow were determined. The McAllister, Grunberg-Nissan and Fang-He correlation equations and Bloomfield-Dewan's model (with residual Gibbs energies calculated using DISQUAC with interaction parameters available in the literature) were applied to iodobenzene, or 1-chloronaphthalene, or 1,2,4-trichlorobenzene, or methyl benzoate or benzene or cyclohexane + n-alkane systems. The dependence of $U_{\text{m,}V}^{\text{E}}$ (isochoric molar excess internal energy) and $Δη$ with $n$ (the number of C atoms of the n-alkane) shows that the fluidization loss of mixtures containing iodobenzene, 1,2,4-trichlorobenzene, or 1-chloronaphthalene when $n$ increases is due to a decrease upon mixing of the number of broken interactions between like molecules. The breaking of correlations of molecular orientations characteristic of longer n-alkanes may explain the decreased negative $Δη$ values of benzene mixtures with $n$ =14,16. The replacement, in this type of systems of benzene by cyclohexane leads to increased positive $Δη$ values, probably due to the different shape of cyclohexane. On the other hand, binary mixtures formed by one of the aromatic polar compounds mentioned above and a short n-alkane show large structural effects and large negative $Δη$ values. From the application of the models, it seems that dispersive interactions are dominant and that size effects are not relevant on $η$ values. The free volume model provides good results for most of the systems considered. Results improve when, within Bloomfield-Dewan's theory, the contribution to $η$ of the absolute reaction rate model is also considered.

physics.chem-ph↗

arXiv2024

Liquid-Liquid Equilibria for Systems Containing 4-Phenylbutan-2-one or Benzyl Ethanoate and Selected Alkanes

Liquid-liquid equilibrium (LLE) phase diagrams have been determined, by means of the critical opalescence method with a laser scattering technique, for the mixtures 4-phenylbutan-2-one + CH$_3$(CH$_2$)$_n$CH$_3$ ($n = 10,12,14$) and for benzyl ethanoate + CH$_3$(CH$_2$)$_n$CH$_3$ ($n = 12,14$). The systems are characterized by having an upper critical solution temperature (UCST), which increases with n. The corresponding LLE curves show a rather horizontal top and become skewed toward higher mole fractions of the polar compound when n is increased. Calorimetric and LLE measurements show that, for mixtures with molecules with a given functional group, interactions between aromatic molecules are stronger than those between homomorphic linear molecules (aromaticity effect). This has been ascribed to proximity effects arising from the presence of the polar group and the aromatic ring within the same molecule. Proximity effects become weaker in the sequence 1-phenylpropan-2-one > 4-phenylbutan-2-one > 1-phenylethanone and are more important in benzyl ethanoate than in ethyl benzoate molecules. Values of the critical compositions and temperatures calculated with the DISQUAC group contribution model are in good agreement with the experimental results. Accordingly, the shape of the LLE curves is also correctly described by DISQUAC.

physics.chem-ph↗

arXiv2024

Thermodynamics of Amide + Amine Mixtures. 2. Volumetric, Speed of Sound and Refractive Index Data for N,N-Dimethylacetamide +N-Propylpropan-1-Amine, +N-Butylbutan-1-Amine, +Butan-1-Amine, or +Hexan-1-Amine Systems at Several Temperatures

Data on density, $ρ$, speed of sound, $c$, and refractive index, $n_{\text{D}}$, of binary systems containing N,N-dimethylacetamide (DMA) + N-propylpropan-1-amine (DPA) or + butan-1-amine (BA) at 293.15 K, 298.15 K and 303.15 K, and + N-butylbutan-1-amine (DBA) or + hexan-1-amine (HxA) at 298.15 K are reported. A densimeter and sound analyzer Anton Paar DSA 5000 has been used for the measurement of $ρ$ and $c$, whereas $n_{\text{D}}$ values have been obtained by means of a refractometer RFM970 from Bellingham+Stanley. Also, values of excess molar volumes, $V_{\text{m}}^{\text{E}}$, excess isentropic compressibilities, $κ_S^{\text{E}}$, excess speeds of sound, $c^{\text{E}}$, excess isobaric thermal expansion coefficients, $α_p^{\text{E}}$, and of excess refractive indices, $n_{\text{D}}^{\text{E}}$, have been determined from these data. The investigated systems are characterized by amide-amine interactions and structural effects, as it is shown by their negative or low positive $V_{\text{m}}^{\text{E}}$ values and by the results from the application of the Prigogine-Flory-Patterson (PFP) model. The breaking of amine-amine interactions is more relevant in systems containing linear primary amines than in those with linear secondary amines, and the $V_{\text{m}}^{\text{E}}$ values are lower for the latter systems. Molar refraction has been used to evaluate the dispersive interactions in the mixtures under study, yielding the result that DPA and HxA systems present similar dispersive interactions and mainly differ in their dipolar character. Steric hindrance of the amide group in DMA leads to weaker amide-amine interactions than in the corresponding N,N-dimethylformamide (DMF) + amine systems.

physics.chem-ph↗

arXiv2024

Thermodynamics of amide + ketone mixtures. 1. Volumetric, speed of sound and refractive index data for N,N-dimethylformamide + 2-alkanone systems at several temperatures

Densities, $ρ$, speeds of sound, $c$, and refractive indices, $n_{\text{D}}$, have been measured for the systems N,N-dimethylformamide (DMF) + propanone, + 2-butanone, or + 2-pentanone in the temperature ($T$) range from 293.15 to 303.15 K and at 298.15 K for the DMF + 2-heptanone mixture. Due to the high volatility of acetone, the corresponding $n_{\text{D}}$ measurements were developed at 293.15 K and 298.15 K. The direct experimental data were used to determine the excess molar volumes, $V_{\text{m}}^{\text{E}}$, and the excess refractive indices, $n_{\text{D}}^{\text{E}}$, at the working $T$. Values of the excess functions at 298.15 K, for the speed of sound, $c^{\text{E}}$, the isentropic compressibility, $κ_S^{\text{E}}$ and for the excess thermal expansion coefficient, $α_p^{\text{E}}$, were also calculated. The investigated systems are characterized by strong amide-ketone interactions, which become weaker when the alkanone size is increased. This is supported by negative $V_{\text{m}}^{\text{E}}$ values; by the dependence on $T$ and pressure of $V_{\text{m}}^{\text{E}}$, and by positive $P_{\text{int}}^{\text{E}}$ (excess internal pressure) values. Analysis of the systems in terms of the Rao's constant indicates that there is no complex formation. In addition, negative $V_{\text{m}}^{\text{E}}$ values also reveal the existence of structural effects, which largely contribute to the excess molar enthalpy, $H_{\text{m}}^{\text{E}}$. $V_{\text{m}}^{\text{E}}$ and $H_{\text{m}}^{\text{E}}$ values increase with the chain length of the 2-alkanone. It allows to conclude that the relative $V_{\text{m}}^{\text{E}}$ variation with the ketone size is closely related to that of the interactional contribution to this excess function. Molar refraction values, $R_{\text{m}}$, show that dispersive interactions become more relevant for the systems including longer 2-alkanones.

physics.chem-ph↗