Volumetric and viscometric properties of binary mixtures of {methyl tert-butyl ether (MTBE) + alcohol} at several temperatures and p = 0.1 MPa: Experimental results and application of the ERAS model

Densities and viscosities of binary mixtures of {methyl tert-butyl ether (MTBE) + methanol, or +ethanol, or +1-propanol, or +2-propanol, or +1-butanol, or +1-pentanol, or +1-hexanol} have been determined as a function of composition at several temperatures and atmospheric pressure. The temperatures studied were (293.15, 298.15, 303.15, and 308.15) K. The experimental results have been used to calculate the excess molar volume $(V_{\text{m}}^{\text{E}})$ and viscosity deviation (Δη). Both $V_{\text{m}}^{\text{E}}$ and Δη values were negative over the entire range of mole fraction for all temperatures and systems studied. Moreover, the $V_{\text{m}}^{\text{E}}$ values have been used to test the applicability of the Extended Real Associated Solution (ERAS) model.     

Thermodynamic study of (heptane + amine) mixtures. III: Excess and partial molar volumes in mixtures with secondary,tertiary, and cyclic amines at 298.15 K

Excess molar volumes V^E at 298.15 K were determined by means of a vibrating tube densimeter for binary mixtures of {heptane + open chain secondary (diethyl to dibutyl) and tertiary (triethyl to tripentyl) amines} as well as for cyclic imines (C₂, C₃, C₄, C₆, and C₇) and primary cycloalkylamines (C₅, C₆, C₇, and C₁₂). The V^E values were found positive for mixtures involving small size amines, with V^E decreasing as the size increases. Negative V^E’s were found for tributyl- and tripentylamine, heptamethylenimine, and cyclododecylamine. Mixtures of heptane with cycloheptylamine showed an s-shaped curve.Partial molar volumes $V^{°}$ of amines at infinite dilution in heptane were obtained from V^E and compared with $V^{°}$ of hydrocarbons and other classes of organic compounds taken from literature. An additivity scheme, based on the intrinsic volume approach, was applied to estimate group (CH₃, CH₂, CH, C, NH₂, NH, N, OH, O, CO, and COO) contributions to $V^{°}$. These contributions, the effect of cyclization on $V^{°}$, and the limiting slope of the apparent excess molar volumes were discussed in terms of solute–solvent and solute–solute interactions.     

Thermodynamic and physicochemical properties of binary mixtures of nitromethane with {2-methoxyethanol + 2-butoxyethanol} systems at T = (293.15, 298.15, 303.15, 308.15, and 313.15) K

The density, relative permittivity, viscosity and speed of sound at T = (293.15, 298.15, 303.15, 308.15, and 313.15) K in the binary mixtures of nitromethane with 2-methoxyethanol and 2-butoxyethanol have been measured as a function of composition. From the experimental results, the excess molar volumes V^E, excess Gibbs free energy of activation for viscous flow $(\mathrm{\Delta }{G}^{1E})$, excess isentropic compressibility $({\kappa }_s^E)$ and the deviations in the relative permittivity, viscosity, and speed of sound from a mole fraction average have been calculated. The viscosity data, at T = 298.15 K, were correlated with equations of Hind et al., Grunberg and Nissan, Frenkel, and McAllister. The results are discussed in terms of intermolecular interactions and structure of studied binary mixtures.     

Volumetric and ultrasonic behaviour of binary mixtures of 1-nonanol with o-cresol,m-cresol,p-cresol and anisole at T = (293.15 and 313.15) K

Densities, ρ, and speeds of sound, u, of binary liquid mixtures of 1-nonanol with o-cresol, m-cresol, p-cresol and anisole have been measured over the entire range of composition at T = (293.15 and 313.15) K and at atmospheric pressure. Using these data, the excess molar volume, V^E, molar free volume, V_f, parameters related to space-filling ability, V_f/V, non-linearity parameters, B/A, isentropic compressibility, κ_S, molar isentropic compressibility, K_S,m, deviation of molar isentropic compressibility, $K_{S\text{,}m}^E$, deviations of the speed of sound, u^D, and limiting excess partial molar volume, ${\overline{V}}_{m\text{,}i}^{E\text{,}0}$, and isentropic compressibility, ${\overline{K}}_{m\text{,}i}^{E\text{,}0}$, have been calculated. The calculated excess and deviation functions have been fitted to the Redlich–Kister polynomial equations and the results analyzed in terms of molecular interactions and structural effects.     

Thermodynamics of solvation of some small peptides in water at T = 298.15 K

The enthalpies of solution in water, Δ_solH_m, of some small peptides, namely the amides of five N-acetyl substituted amino acids of glycine, l-alanine, l-proline, l-valine, l-leucine and two cyclic anhydrides of glycine and l-sarcosine (diketopiperazines), were measured by isothermal calorimetry at T = (296.84, 306.89, and 316.95) K. The enthalpies of solution at infinite dilution at T = 298.15 K were derived and added to the enthalpies of sublimation, ${\mathrm{\Delta }}_{\mathrm{sub}}{H}_{\mathrm{m}}^{\circ }$, at the same temperature, to obtain the corresponding solvation enthalpies at infinite dilution, ${\mathrm{\Delta }}_{\mathrm{solv}}{H}_{\mathrm{m}}^{\infty }$. Moreover, the partial molar heat capacities at infinite dilution at T = 298.15 K, $C_{p\text{,}2}^{\infty }$, were calculated by adding molar heat capacities of solid small peptides, C_p,m(cr), to the ${\mathrm{\Delta }}_{\mathrm{sol}}{C}_{p\text{,}\mathrm{m}}^{\infty }$ values obtained from our experimental data. CH₂ group contributions, in terms of solvation enthalpy and partial molar heat capacity, were −3.2 kJ · mol⁻¹ and 89.3 J · K⁻¹ · mol⁻¹, respectively, in good agreement with the literature data. Simple additive methods were used to estimate the average molar enthalpy of solvation and partial molar heat capacity at infinite dilution for the 1/2CONH⋯CONH functional group in the small peptides. Values obtained were −46.7 kJ · mol⁻¹ for solvation enthalpy and −42.4 J · K⁻¹ · mol⁻¹ for partial molar heat capacity, significantly lower than values obtained for the CONH functional group in monofunctional model compounds.