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 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 molar enthalpies of triethylamine + ethylbenzene, + n-propylbenzene, + n-butylbenzene, + isopropylbenzene,and + isobutylbenzene at 303.15 K

Excess molar enthalpies H_m^E of triethylamine + ethylbenzene, + n-propylbenzene, + n-butylbenzene, + isopropylbenzene, and + isobutylbenzene were measured over the entire composition range at 303.15 K with an LKB flow microcalorimeter. H_m^E values are positive and decrease with increasing chain length of the alkylbenzene.     

Excess volumes of binary mixtures of (p-xylene+an n-alkane)

A semi-continuous dilatometer for measuring excess volume is described. Excess volumes of p-xylene +n-hexane + n-octane, +n-decane, +n-dodecane, +n-tetradecane, and +n-hexadecane have been measured at 298.15 K as a function of composition.     

p, T, x, y data of benzene + n-hexane and cyclohexane + n-heptane systems

The isothermal vapour—liquid equilibria of the benzene + n-hexane and cyclohexane + n-heptane systems have been studied using a dynamic method. The thermodynamic consistency of the data has been tested and the prediction from several empirical and semitheoretical models have been compared with the experimental values of different excess properties.     

Thermodynamics of binary mixtures containing aldehydes. excess enthalpies of n-alkanals + benzene and + tetrachloromethane mixtures

Molar excess enthalpies H^E have been measured as a function of mole fraction at atmospheric pressure and 298.15 K for the binary liquid mixtures of ethanal, propanal, butanal and pentanal + benzene or + tetrachloromethane. The results show that the excess enthalpies decrease with increasing the n-alkanal chain length, with negative values for n-pentanal.     

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.     

Speeds of sound and isentropic compressibilities of binary mixtures containing trialkylamines with alkanes and mono-alkylamines at 303.15 and 313.15 K

Isentropic compressibilities κ_S, and excess isentropic compressibilities κ_S^E have been determined from measurements of speeds of sound u and densities ρ of 14 binary mixtures of triethylamine (TEA) and tri-n-butylamine (TBA) with n-hexane, n-octane, iso-octane, n-propylamine, n-butylamine, n-hexylamine and n-octylamine. The relative magnitude and sign of κ_S^E have been interpreted in terms of molecular interactions and interstitial accommodation. The values of κ_S^E for TEA + alkane are positive while for TBA + alkane are negative. The values of κ_S^E for TEA + primary amine become progressively less positive and eventually to negative with the increase in chain length of alkylamine. In case of TBA + primary amine, the values of κ_S^E increase from n-propylamine to n-butylamine, and then decrease with chain length of primary amine. The experimental speeds of sound u have been analyzed in terms of collision factor theory, free length theory and Prigogine–Flory–Patterson statistical theory of solutions.     

Excess molar volumes and viscosities of binary mixtures of cyclohexane and n-alkane at 298.15 K

Awwad, A.M. and Salman, M.A., 1986. Excess molar volumes and viscosities of binary mixtures of cyclohexane and n-alkane at 298.15 K. Fluid Phase Equilibria, 25: 195-208.Excess molar volumes, viscosities, excess molar viscosities, and excess molar activation energies of viscous flow were determined for binary mixtures of cyclohexane + n-pentane, + n-hexane, + n-heptane, + n-octane, + n-nonane, + n-decane, + n-dodecane, + n-tetradecane and + n-hexadecane at 298.15 K. The effect of orientational order of n-alkane on solution molar volumes and viscosities is investigated as well as the adequacy of the Flory theory and free volume theories used to predict solution molar volumes and viscosities. For longer n-alkanes V^E, η^E and ΔG*^E are positive and associated with the orientational order.     

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.     

Densities and excess molar volumes of the ternary mixture (1-butanol+n-hexane+1-chlorobutane) at 298.15 and 313.15 K. Application of the ERAS model

Densities of the liquid mixtures (n-hexane+1-chlorobutane) and (1-butanol+n-hexane+1-chlorobutane) have been measured by the vibrating tube technique at 298.15 K and 313.15 K. With these densities, excess molar volumes were calculated. An extended version of the so-called ERAS model has been used for describing V^E of the complete ternary system at 298.15 K. Qualitatively the ERAS-model gives an adequate representation of this system, being similar the shapes of both the experimental and the predicted curves.     

ESR spectra and structure of the n-butane and n-hexane radical cations

Well-resolved ESR spectra of the n-butane and n-hexane radical cations have been generated, each spectrum showing a 1:2:1 triplet and a detailed substructure. The results are interpreted in terms of an a_g singly occupied MO (^σC—C, δC–H_ax) which is delocalized over the extended carbon chain (C_2h symmetry) and two axial hydrogens.     

The vapour pressure behaviour and the association of N-methylethylamine,diethylamine and their N-deuterioanalogues in mixtures with n-hexane

The vapour pressure isotherms of mixtures of N-methylethylamine and N-methyl(N-²H)ethylamine with n-hexane have been measured between 273 and 323 K. The vapour pressure isotherms of mixtures of diethylamine and (N-²H)diethylamine with nhexane between 293 and 353 K have also been measured. In addition, the vapour pressures of the pure amines have been determined down to 228 or 243 K. As evidenced by the small values for the Wilson coefficients, the activity coefficients, the Gibbs free energies and the data derived from the theory of ideal associated solutions, the association of diethlamine is very weak; that of N-methylethylamine is not much larger. The observations on the vapour pressure isotope effect of the two amines and their N-deuterioanalogues are compatible with this interpretation. The normal effect is smaller for diethylamine, with ratios P_D/P_H of 0.972–0.997 between 243 and 323 K, than for N-methylethylamine with values of 0.965–0.991, and the partial pressure quotients calculated for mixtures of the two compounds with n-hexane show the transition from the normal to the inverse effect on low dilution. The data for the N-deuterioanalogues and their mixtures with n-hexane suggest a somewhat greater energy of the deuterium bonds.     

Vapour-liquid equilibria. I. An apparatus for isothermal total vapour pressure measurements: Binary mixtures of ethanol and t-butanol with n-hexane, n-heptane and n-octane at 313.15 K

A static apparatus for the determination of total vapour pressure isotherms of mixtures is described. The apparatus works without a null manometer, and degassing of samples is done without freezing. VLE data for six binary mixtures of ethanol and t-butanol with n-hexane, n-heptane and n-octane are reported and compared with literature data. References to other VLE data obtained using this apparatus are also given.     

Air/water partition coefficients for normal alkanes (n-pentane to n-nonane)

Consistent values of the air/water partition coefficient for n-pentane, n-hexane, n-heptane, n-octane and n-nonane have been measured in the temperature range 15–35°C. All of the results may be summarised by an equation derived on the basis of thermodynamic principles. The constants of this equation have been determined by least-squares regression. The solubilities of hydrocarbons in water as well as thermodynamic quantities relating to the solvation process can be predicted using the equation.     

Refractive Indices Measurement and Correlation for Selected Binary Systems of Various Polarities at 25 °C

New refractive indices at 25 °C were measured and are reported here for 19 binary mixtures of pentan-3-one+1,2-dichloroethane, +1,3-dichloropropane, +1,4-dichlorobutane, +trichloromethane, +1,1,1-trichloroethane, +1,1,2,2-tetrachloroethane; cyclopentanone+1-chlorobutane, +1,1,2,2-tetrachloroethane; cyclohexanone+1,1,2,2-tetrachloroethane; 5-chloro-2-pentanone+n-hexane, +toluene, +ethylbenzene; nitromethane+trichloromethane; and nitromethane or nitroethane, +1,2-dichloroethane, +1,3-dichloropropane, +1,4-dichlorobutane. The experimental refractive index deviations from linear mixing behavior have been evaluated and correlated consistently with the 3-parameter Redlich–Kister equation with good results. The molar refraction was also examined for the systems including pentan-3-one, cyclopentanone, cyclohexanone and 5-chloro-2-pentanone for which densities and excess molar volumes are available from previous works. Different theoretical (n, ρ) mixing rules were tested for these systems. The excess Gibbs energy G ^E and excess enthalpy H ^E values were considered together with the excess molar volumes V ^E, excess refractive indexes $ n_{\text{D}}^{\text{E}} $ , molar refraction R and excess molar refractions R ^E on mixing in the discussion of the influence of the alkyl chain length or of the nature of the second component in the mixture in terms of molecular interactions.     

Distribution of pesticides in n-hexane/water and n-hexane/acetonitrile systems and estimation of possibilities of their extraction isolation and preconcentration from various matrices

Distribution of 150 most widely used pesticides of different chemical classes (amides, anilinopirimidines, aromatics, benzenesulfonates, carbamates, dicarboximides, organophosphorus compounds, phenyl esters, phenylureas, pyrazoles, pyrethroids, pyrimidines, strobilurins, sulfamides, triazines, triazoles, etc.) in n-hexane/water and n-hexane/acetonitrile systems was investigated at 25 °C. Distribution constants of pesticides (P) have been calculated as ratio of pesticide concentration in n-hexane to its concentration in water or acetonitrile phase. HPLC and GC methods were used for pesticides determination in phases. It was found that the overwhelming majority of pesticides are hydrophobic, i.e. in n-hexane/water system Lg P ? 0, and the difference in Lg P values can reach 9.1 units. Replacement of water for acetonitrile leads to dramatic fall of Lg P values reaching 9.5 units. The majority of Lg P values in this case are negative and their differences is strongly leveled in comparison with a hexane/water system. Thus, maximal difference in pesticides Lg P values for n-hexane/acetonitrile system is 3.2 units. It is shown that n-hexane can be used for selective and efficient extraction and preconcentration of pesticides from water matrices. On the other hand, acetonitrile is effective for the isolation and preconcentration of pesticides from hydrocarbon and vegetable oil matrices. The distribution constants described in the paper may be effectively used for the estimation of possibilities of extraction isolation, preconcentration and separation of pesticides.     

Excess Gibbs free energies of mixtures of tetrakis(2-ethylbutoxy)silane + cyclohexane, + benzene,and + carbon tetrachloride at 308.15 K

The excess Gibbs free energies G^E for tetra(2-ethylbutoxy)silane (tkebs) + cyclohexane, + benzene, and + carbon tetrachloride have been measured at 308.15 K with a new vapour-pressure apparatus. For tkebs + cyclohexane, G^E is negative with a minimum value of ?538 J mol^?1 near x₂(tkebs) = 0.39. For tkebs + benzene, the minimum value of G^E is ?453 J mol^?1 near x₂ = 0.41, and for tkebs + carbon tetrachloride, G^E has a minimum value of ?715 J mol^?1 near x₂ = 0.39.