Calorimetric effects of short-range orientational order in solutions of benzene or n-alkylbenzenes in n-alkanes

A Picker flow microcalorimeter was used to determine molar excess heat capacities, C^E_p, at 298.15 K, as function of concentration, for the eleven liquid mixtures: benzene+n-tetradecane; toluene+n-heptane, and +n-tetradecane; ethylbenzene+n-heptane, +n-decane, +n-dodecane; and +n-tetradecane; n-propylbenzene +n-heptane, and +n-tetradecane; n-butylbenzene+n-heptane, and +n-tetradecane. In addition, molar excess volumes, V^E, at 298.15 K, were obtained for each of these systems (except benzene+n-tetradecane) and for toluene+n-hexane. The excess volumes which are generally negative with a short alkane, increase and become positive with increasing chain length of the alkane. The excess heat capacities are negative in all cases. The absolute ¦C^E_p¦ increased with increasing chain length of the n-alkane. A formal interchange parameter, C_p12, is calculated and its dependence on n-alkane chain length is discussed in terms of molecular orientations.     

The thermodynamics of a cycloalkane + an n-alkane

The excess volumes of cyclopentane + n-hexane, + n-heptane, n-dodecane; cyclohexane + n-pentane; cycloheptane+ n-pentane, n-octane and n-dodecane have been measured at two temperatures. The results together with literature values reported for other systems of the type cycloalkane + an n-alkane have been discussed and the trends highlighted.V^E_m and H^E_m results from our work and from the literature, for the systems cyclopentane or cyclohexane + an n-alkane, have been analysed in the light of the statistical theory of Flory.     

Excess molar volumes of (ethyl formate or ethyl acetate + an isomer of hexanol) at 298.15 K

Excess molar volumes V_m^E were determined over the entire composition range at 298.15 K for ethyl formate or ethyl acetate + hexan-1-ol, +2-methylpentan-1-ol, +3-methylpentan-2-ol, +2-methylpentan-3-ol, +3-methylpentan-3-ol, +2-methylpentan-2-ol, +4-methyl-pentan-2-ol, and +hexan-2-ol. Excess volumes were determined from density measurements made with a vibrating-tube densimeter. The V_m^E values were all positive, decreasing with the n value of the ester: C_n?1H_2n?1CO₂C₂H₅.     

Excess volumes for trichloroethene + benzene, + toluene, + p-xylene, + tetrachloromethane,and + trichloromethane at 303.15 K

Excess volumes V^E for trichloroethene (CCl₂CHCl) + benzene, + toluene, + p-xylene, + tetrachloromethane, and + trichloromethane have been measured at 303.15 K, by direct dilatometry. V^E has been found to be positive for trichloroethene + benzene, and + trichloromethane, and negative for trichloroethene + toluene, and + p-xylene. For trichloroethene + tetrachloromethane V^E is positive at low mole fractions of C₂HCl₃ and negative at high mole fractions.     

Excess Molar Volumes of n-Pentanol + Cumene,n-Pentanol + 1,4-Dioxane and Cumene + 1,4-Dioxane at Different Temperatures

Abstract

Molar excess volumes (V^E ) and partial molar excess volumes ( ^VE ) are reported for non-electrolyte binary mixtures of n-pentanol + cumene, n-pentanol + 1,4-dioxane and cumene + 1,4-dioxane at four temperatures and over the whole concentration range. In these systems, the n-pentanol is a highly polar molecule with association in its pure state, while the others two show little polarity without association in their pure states. The results of V^E are discussed in terms of the interactions between components. The Prigogine–Flory–Patterson model of solution thermodynamics has been used to predict V^E . This work shows the importance of the three contributions δV _int, δV _p? and δV_F to V^E .     

Excess volumes and isobaric heat capacities of diisopropyl ether with several alkanols at 298.15 K: Application of the symmetrical extended real associated solution model

Excess molar volumes v^E and isobaric heat capacities C_p^E at 298.15 K were measured for 11 mixtures of diisopropyl ether (DIPE)+alcohol (from methanol to 1-undecanol), DIPE with n-heptane and 2,4-dimethylpentane with 1-octanol. Moreover the excess molar enthalpy h^E of DIPE with n-heptane at the same temperature was also measured in order to obtain the self-association parameters of the symmetrical extended real associated solution (SERAS) model for DIPE. Parameters of the SERAS model corresponding to the interaction of DIPE with each alcohol were obtained by fitting v^E data reported here and h^E data taken from a previous work. The results obtained are compared with those from the literature obtained by using the ERAS model in the traditional way for several of the studied mixtures. C_p^E curves are qualitatively explained in terms of the SERAS model.     

Molar heat capacity of binary liquid mixtures: 1,2-dichloroethane + cyclohexane and 1,2-dichloroethane + methylcyclohexane

The molar heat capacity at constant pressure, C_P, of the two binary liquid mixtures 1,2-dichloroethane + cyclohexane and 1,2-dichloroethane + methylcyclohexane were determined at 298.15 K from measurements of the volumetric heat capacity, C_P/V, in a Picker flow microcalorimeter (V is the molar volume). For the molar excess heat capacity, C_P^E, the imprecision of the adopted stepwise procedure is characterized by a standard deviation of about ± 0.05 J K^?1 mole^?1, which amounts to ca. 3% of C_P^E. Literature data on ultrasonic velocities, on molar volumes, and on coefficients of thermal expansion were used to calculate the molar heat capacity at constant volume, C_v, and the isothermal compressibility, β_T, of the pure substances, as well as the corresponding excess quantities C_V^E and (Vβ_T)^E of the binary mixture 1,2-dichloroethane + cyclohexane. A preliminary discussion of our results in terms of external and internal rotational behavior (trans-gauche equilibrium of 1,2-dichloroethane) is presented.     

Excess heat capacities and excess volumes of binary liquid mixtures of 1,1,1,-trichloroethane with cyclic ethers at 298.15 K

Measurements of volumetric heat capacities at constant pressure, C_p/V (V being the molar volume), at 298.15 K, of the binary liquid mixtures 1,1,1-trichloroethane + oxolane, +1,3-dioxolane, +oxane, +1,3-dioxane, and +1,4-dioxane were carried out in a Picker-type flow microcalorimeter. Molar heat capacities at constant pressure. C_p, and molar excess heat capacities, C^E_p, were calculated from these results as a function of the mole fraction. C^E_p values for these systems are positive and the magnitude depends on the size of the cycle and on the relative position of the oxygen atoms in the cyclic diethers. The precision and accuracy for C^E_p are estimated as better than 2%. Molar excess volumes, V^E, for the same systems, at 298.15 K, have been determined from density measurements with a high-precision digital flow densimeter. The experimental results of V^E and C^E_p, are interpreted in terms of molecular interactions.     

Thermodynamics of molecular interactions in binary mixtures of non-electrolytes. Molar excess volumes

Molar excess volumes, V^E, for pyridine (A) + α-picoline (B), + β-picoline (B) and + γ-picoline (B) and benzene (A) + toluene (B), + o-xylene (B) and + p-xylene (B) and carbon tetrachloride (A) + n-heptane (B) have been measured dilatometrically as a function of temperature and composition and have been utilized to study B—B and B—B—B interactions in the presence of A via the Mayer—McMillan approach. A model has also been presented to account for these B—B and B—B—B interactions. The V^E data at 308.15 K have also been analysed in terms of the “graph theoretical” approach which describes the V^E data well for all these mixtures at 308.15 K. The “graph theoretical” approach has further been extended to successfully evaluate V^E data for a mixture at any temperature, T₂, when the V^E data at T₁ are known.     

Volume changes on mixing perfluoroalkanes with alkanes or ethers at 298.15 K

Excess molar volumes V^E at 298.15 K have been determined by means of a vibrating-tube densimeter for binary mixtures of n-hexane with a perfluoroalkane, C₅–C₈, and of perfluorohexane with a n-alkane, C₅–C₈, or an ether (diethyl, dipropyl, dibutyl, butyl methyl, and butyl ethyl ether). The systems perfluoropentane+hexane, perfluorohexane+pentane or hexane or diethyl ether have been investigated in the entire mole fraction range, while the other mixtures only in the miscibility regions. The observed V^E values are positive (up to 5.5 cm³ mol⁻¹) and among the largest known for non-electrolyte systems. Limiting partial molar volumes, $\text{V}\text{̄}\text{°}$, have been evaluated for each component of the examined mixtures. The behaviour of $\text{V}\text{̄}\text{°}$ has been discussed in terms of the scaled particle theory (SPT) and of a simple group additivity scheme based on surface interactions. An estimate has been made of the average separation distance of solvent from solute molecules.     

Excess enthalpies of some aromatic aldehydes in n-hexane, n-heptane and benzene

Calorimetric measurements of molar excess enthalpies, H^E, at 298.15 K, of mixtures containing aromatic aldehydes of general formula C₆H₅(CH₂)_mCHO (with m = 0, 1 and 2) + n-hexane, n-heptane or benzene are reported, together with the values of H^E at equimolar composition compared with the corresponding values of H^E for the aromatic ketones in the same solvents. The experimental results clearly indicate that the intermolecular interactions between the carbonyl groups (CHO) are influenced by the intramolecular interactions between the carbonyl and phenyl groups, particularly for the mixtures containing benzaldehyde.     

Excess heat capacities of binary mixtures of carbon tetrachloride with n-alkanes at 298.15 K

A Picker flow microcalorimeter was used to determine molar excess heat capacities C_P^E at 298.15 K for mixtures of carbon tetrachloride + n-heptane, n-nonane, and n-decane. The excess heat capacities are negative in all cases. The absolute value |C_P^E| increases with increasing chain length of the alkane. A formal interchange parameter, c_P12, is calculated and its dependence on n-alkane chain length is discussed briefly in terms of molecular orientations.     

Thermodynamic study of (heptane + amine) mixtures. II. Excess and partial molar volumes 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 + primary n-alkyl (C₃ to C₁₀) and branched amines (iso-propyl-, iso-, sec-, and tert-butyl-, iso-, tert-pentyl-, and pentan-3-amine) in the whole composition range. The apparent molar volumes of solid dodecyl- and tetradecylamine in heptane dilute solution were also determined. The V^E values were found positive for mixtures involving C₃ to C₈ linear amines, with V^E decreasing with chain lengthening. Heptane + nonyl and decylamine showed s-shaped, markedly asymmetric, curves. Mixtures with branched C₃ to C₅ amines displayed positive V^E’s larger than those observed in the mixtures of the corresponding linear isomers. Partial molar volumes V° at infinite dilution in heptane were evaluated for the examined amines and compared with those of alkanes and alkanols taken from the literature. An additivity scheme, based on the intrinsic volume approach, was applied to estimate group (CH₃, CH₂, CH, C, NH₂, and OH) contributions to V°. The effect of branching on V° and the limiting slope of the apparent excess molar volumes were evaluated and discussed in terms of solute–solvent and solute–solute interactions.     

Excess molar quantities of (a halogenated n-alkane + an n-alkane) A comparative study of mixtures containing either 1-chlorobutane or 1,4-dichlorobutane

Excess molar volumes V_m^E at 298.15 K were obtained, as a function of mole fraction x, for series I: {x1-C₄H₉Cl + (1 ? x)n-C_lH_{2l + 2}}, and II: {x1,4-C₄H₈Cl₂ + (1 ? x)n-C_lH_{2l + 2}}, for l = 7, 10, and 14. 10, and 14. The instrument used was a vibrating-tube densimeter. For the same mixtures at the same temperature, a Picker flow calorimeter was used to measure excess molar heat capacities C_{p, m}^E at constant pressure. V_m^E is positive for all mixtures in series I: at x = 0.5, V_m^E/(cm³ · mol^?1) is 0.277 for l = 7, 0.388 for l = 10, and 0.411 for l = 14. For series II, V_m^E of {x1,4-C₄H₈Cl₂ + (1 ? x)n-C₇H₁₆} is small and S-shaped, the maximum being situated at x_max = 0.178 with V_m^E(x_max)/(cm³ · mvl^?1) = 0.095, and the minimum is at x_min = 0.772 with V_m^E(x_min)/(cm³ · mol^?1) = ?0.087. The excess volumes of the other mixtures are all positive and fairly large: at x = 0.5, V_m^E/(cm³ · mol^?1) is 0.458 for l = 10, and 0.771 for l = 14. The C_{p, m}^Es of series I are all negative and |C_{p, m}^E| increases with increasing l: at x = 0.5, C_{p, m}^E/(J · K^?1 · mol^?1) is ?0.56 for l = 7, ?1.39 for l = 10, and ?3.12 for l = 14. Two minima are observed for C_{p, m}^E of {x1,4-C₄H₈Cl₂ + (1 ? x)n-C₇H₁₆}. The more prominent minimum is situated at x′_min = 0.184 with C_{p, m}^E(x′_min)/(J · K^?1 · mol^?1) = ?0.62, and the less prominent at x″_min = 0.703 with C_{p, m}^E(x″_min)/(J · K^?1 · mol^?1) = ?0.29. Each of the remaining two mixtures (l = 10 and 14) has a pronounced minimum at low mole fraction (x_min = 0.222 and 0.312, respectively) and a broad shoulder around x = 0.7.     

Volumes of mixing of n-octylacetate + n-alkanes: an interpretation in terms of the Prigogine-Flory-Patterson theory

The results of measurements of molar excess volumes V^E at 303.15 K over the whole mole fraction range for eight mixtures: n-octylacetate + n-hexane; +n--heptane; + n-octane; +nn-nonane; + n-decane; +nn-dodecane; + n-tetradecane and + n-hexadecane are presented. The experimental values of V^E show a regular pattern of behaviour for the eight sets of binary mixtures. The magnitude of V^E for this class of mixtures decreases as the n-alkane chain-length decreases. In order to explain the observed behaviour, the Prigogine-Flory-Patterson theory is used to predict the total V^E and the three different contributions to V^E. Agreement between the theoretical and experimental V^E is reasonable for the eight systems     

Liquid Solution Densities of Ternary-Pseudobinary Mixtures of (Benzene + Cyclohexane) in the Presence of Tetrachloromethane or <Emphasis Type="Italic">n</Emphasis>-Hexane

Densities have been obtained as a function of composition for ternary-pseudobinary mixtures of [(benzene + tetrachloromethane or n-hexane) + (cyclohexane + tetrachloromethane or n-hexane)] at atmospheric pressure and the temperature 298.15 K, by means of a vibrating-tube densimeter. Excess molar volumes, V_m^E, partial molar volumes and excess partial molar volumes were calculated from the density data. The values of V_m^E have been correlated using the Redlich–Kister equation and the coefficients and standard errors were estimated. The experimental and calculated quantities are used to discuss the mixing behavior of the components. The results show that the third component, CCl₄ or n-C₆H₁₄, have quite different influences on the volumetric properties of binary liquid mixtures of benzene with cyclohexane.     

Excess molar volumes of methylcyclohexane+benzene, +methylbenzene, +1,4-dioxane,and +tetrahydrofuran at 303.15 K

Excess molar volumes V_m^E as function of mole fraction x for methylcyclohexane + benzene, + methylbenzene, + 1,4-dioxane, and + tetrahydrofuran are reported at 303.15 K. The excess molar volumes are positive and indicate the presence of weak interactions.     

Excess molar volumes at 298.15 K of binary liquid organic mixtures containing n-alkanones and linear ethers: Application of Flory’s theory

Excess molar volumes, V_m^E, at 298.15 K and atmospheric pressure over the entire composition range for binary mixtures of 2-butanone with di-n-butyl ether and 2-pentanone and 3-pentanone with di-n-butyl ether and 2,5-dioxahexane, 2-heptanone and 4-heptanone with di-n-butyl ether, 2,5-dioxahexane and 3,6,9-trioxaundecane are reported from densities measured with a vibrating-tube densimeter. All the excess volumes present strong contractions when compared to those of n-alkanone+n-alkane systems.Molar excess enthalpies H_m^E and V_m^E of the considered mixtures vary similarly. This may be attributed to interactional effects which prevail over structural effects.Flory’s theory has been applied to the systems under study. As expected, results for H_m^E are better when the difference in polarity of the components of the mixture decreases. V_m^E is often poorly represented.     

Excess molar volumes and dynamic viscosities for binary mixtures of toluene + n-alkanes (C5–C10) at T = 298.15 K – Comparison with Prigogine–Flory–Patterson theory

Densities ρ, dynamic viscosities η, for binary mixtures of toluene with some n-alkanes, namely, n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane have been measured over the complete composition range. Excess molar volumes V^E, viscosity deviations Δη, and excess Gibbs free energy of activation ΔG^1E, were calculated there from and were correlated by Redlich–Kister type function in terms of mole fractions. For mixtures of toluene with n-pentane and n-hexane the V^E is negative and for the remaining systems is positive. The Δη values are negative for all the studied mixtures. The ΔG^1E values shows the positive values for the binary mixtures with n-decane, whereas the negative values have been observed for all the remaining binary mixtures. From the results, the excess thermal expansivities at constant pressure α^E, is also estimated. The Prigogine–Flory–Patterson (PFP) theory and its applicability in predicting V^E is tested. The results obtained for viscosity of binary mixtures were used to test the semi-empirical relations of Grunberg and Nissan, Tamura and Kurata, Hind et al., Katti and Chaudhri, McAllister, Heric, Kendall, and Monroe. The experimental on the constituted binaries are analyzed to discus the nature and strength of intermolecular interactions in these mixtures.