N. Riesco

Thermodynamics of mixtures with strongly negative deviations from Raoult’s law. Part 8. Excess molar volumes at 298.15 K for 1-alkanol + isomeric amine (C6H15N) systems ☆: Characterization in terms of the ERAS model

Excess molar volumes, VEm, at 25°C and atmospheric pressure, over the entire composition range for binary mixtures of methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, and 1-octanol with-methylbutylamine are reported. They are calculated from densities measured with a vibrating-tube densimeter. All the excess volumes are large and negative over the entire composition range. This indicates strong interactions between unlike molecules, which are greatest for the system involving methanol, characterized by the most negative VEm. For the other solutions, VEm at equimolar composition, is approximately the same. The VEm curves vs. mole fraction are nearly symmetrical. The ERAS model is applied to 1-alkanol + N-methylbutylamine, and 1-alkanol + diethylamine systems. The ERAS parameters confirm that the strongest interactions between unlike molecules are encountered in solutions with methanol. The model consistently describes VEm and excess molar enthalpies HEm of the mixtures studied.

Thermodynamics of organic mixtures containing amines - III: Molar Excess Volumes at 298.15 K for Tripropylamine +n‐Alkane Systems ‐ Application of the Flory Theory to N,N,N‐Trialkylamine + n‐Alkane Mixtures

Molar excess volumes at 298.15 K and atomospheric pressure for tripropylamine + n-hexane, + n-octane, + n-decane, + n-dodecane or + n hexadecane systems determined from densities measured with an Anton-Paar DMA 602 vibrating-tube densimeter are reported. N,N,N-trialkylamine + n-alkane systems have been studied using the Flory theory. Better results on excess enthalpies are obtained when the difference in size between the mixture components is large. The dependence of the excess volume at equimolar composition with the length of the n-alkane is correctly described. The simultaneous analysis of the experimental excess volumes and of the excess enthalpies reveal that free volume effects are important in systems formed by triethylamine or tripropylamine and longer alkanes, as well as in those involving tripropylamine or tributylamine and the shorter alkanes. The Patterson effect is present in the studied mixtures. The more globular amines, triethylamine, tripropylamine or tributylamine are order breakers of the longer alkanes. The amines of very large size, e.g., tridodecylamine, show an ordered structure.

Thermodynamics of Organic Mixtures Containing Amines. II. Excess Molar Volumes at 25°C for Methylbutylamine + Alkane Systems and Eras Characterization of Linear Secondary Amine + Alkane Mixtures

Excess molar volumes, at 25°C and atmospheric pressure for methylbutyl amine + n-hexane; + cyclohexane; + n-octane; n-decane; + n-dodecane; + n-tetradecane, or + n-hexadecane systems are reported from densities measured with a vibrating-tube densimeter. The excess functions, molar enthalpy, and volume, for linear secondary amine + n-alkane systems are discussed in terms of interactional and structural effects. In addition, these solutions, which include amines from dimethyl to dioctylamine, are studied in the framework of the ERAS model. The corresponding ERAS parameters are reported. The agreement between experimental data and ERAS results is good for excess enthalpies, excess Gibbs energies, and excess molar volumes. The larger discrepancies are found for the excess volumes when strong free-volume effects are present in the investigated mixtures. The variation with temperature of the thermodynamic properties is well described by ERAS.

Thermodynamics of mixtures containing a very strongly polar compound: IV – application of the DISQUAC, UNIFAC and ERAS models to DMSO+ organic solvent systems

Binary mixtures of dimethylsulfoxide (DMSO) with alkane, benzene, toluene 1-alkanol, or 1-alkyne have been investigated in terms of DISQUAC. The corresponding interaction parameters are reported. ERAS parameters for 1-alkanol + DMSO mixtures are also given. ERAS calculations were developed considering DMSO as a not self-associated compound. DISQUAC represents fairly well a complete set of thermodynamic properties: molar excess enthalpies, molar excess Gibbs energies, vapor–liquid equilibria, natural logarithms of activity coefficients at infinite dilution, or partial molar excess enthalpies at infinite dilution. DISQUAC improves UNIFAC calculations for H E . Both models yield similar results for VLE. In addition, DISQUAC also improves, ERAS results for 1-alkanol + DMSO mixtures. This may be due to ERAS cannot represent the strong dipole–dipole interactions present in such solutions.

DISQUAC characterization of mixtures containing alkynes and alkanes or 1-alkanols. Comparison with ERAS model

Abstract Mixtures formed by alkynes and n -alkanes, cycloalkanes or 1-alcohols have been examined in the framework of the DISQUAC group contribution model. The corresponding interaction parameters are reported. These ones follow some simple rules: (a) the quasichemical (QUAC) interchange coefficients for the aliphatic/acetylene contacts are independent of the alkyne; (b) the dispersive (DIS) parameters for such contacts when isomeric non-terminal alkynes are involved are also independent of the alkyne; (c) in 1-alkanols+alkynes mixtures, the QUAC parameters for the hydroxyl/acetylenic contacts do not depend on the mixture compounds. Thermodynamic properties such as vapor–liquid equilibria (VLE), including coordinates of azeotropes or activity coefficients at infinite dilution ( γ i ∞ ), and excess molar enthalpies ( H E ) are correctly described by DISQUAC. The model can be applied over a wide range of temperature. 1-Alkanols+1-alkynes, or + 3-hexyne systems have been also characterized in terms of the ERAS model. Calculations were developed neglecting the possible self-association of 1-alkynes. This is reasonable in view of the good results provided by DISQUAC (a purely physical model), and of the very low values of the equilibrium constants obtained from the ERAS model when analyzing 1-alkynes+ n -alkanes mixtures. ERAS results on H E are improved by DISQUAC. Both models provide similar results on excess molar Gibb’s energies ( G E ) of 1-alkanols + 3-hexyne mixtures. Excess molar volumes of solutions containing 1-alkanols and 1-alkynes are represented qualitatively by ERAS. Interactions in the treated solutions are analyzed in terms of the effective dipole moment ( μ ). So, the higher H E of 1-alkynes + n -alkanes mixtures compared to that of non-terminal isomeric alkynes + n -alkanes solutions may be attributed to the higher μ of 1-alkynes. Structural effects are also relevant. In 1-alkanols + 1-alkynes systems, interactions between unlike molecules become weaker with the size increase of the mixture components.

Thermodynamics of mixtures containing ethers PART II: Isothermal x–y data for the ternary system MTBE + methanol + 1-butanol and for two constituent binaries: DISQUAC predictions on VLE of ternary mixtures containing tertiary-alkyl ethers and organic solvents

Authors acknowledge the European Commission for the financial support by contract no. ECSC 7220-PR/048. M.C.M. and M.T.I. are thankful to the Ministry of Science and Technology.