Molecular Interactions in 1-Ethyl-3-Methylimidazolim Tetrafluoroborate + Amide Mixtures: Excess Molar Volumes, Excess Isentropic Compressibilities and Excess Molar Enthalpies

The densities, ρ ₁₂, and speeds of sound, u ₁₂, of 1-ethyl-3-methylimidazolium tetrafluoroborate (1) + N-methylformamide or N,N-dimethylformamide (2) binary mixtures at (293.15. 298.15. 303.15, 308.15 K), and excess molar enthalpies, $ H_{12}^{\text{E}} $ H 12 E , of the same mixtures at 298.15 K have been measured over the entire mole fraction range using a density and sound analyzer (Anton Paar DSA-5000) and a 2-drop microcalorimeter, respectively. Excess molar volume, $ V_{12}^{\text{E}} $ V 12 E , and excess isentropic compressibility, $ \left( {\kappa_{S}^{\text{E}} } \right)_{12} $ ( κ S E ) 12 , values have been calculated by utilizing the measured density and speed of sound data. The observed data have been analyzed in terms of: (i) Graph theory and (ii) the Prigogine–Flory–Patterson theory. Analysis of the $ V_{12}^{\text{E}} $ V 12 E data in terms of Graph theory suggest that: (i) in pure 1-ethyl-3-methylimidazolium tetrafluoroborate, the tetrafluoroborate anion is positioned over the imidazoliun ring and there are interactions between the hydrogen atom of (C–H{edge}) and proton of the –CH₃ group (imidazolium ring) with fluorine atoms of tetrafluoroborate anion, and (ii) (1 + 2) mixtures are characterized by ion–dipole interactions to form a 1:1 molecular complex. Further, the $ V_{12}^{\text{E}} $ V 12 E , $ H_{12}^{\text{E}} $ H 12 E and $ \left( {\kappa_{S}^{\text{E}} } \right)_{12} $ ( κ S E ) 12 values determined from Graph theory compare well with their measured experimental data.     

Excess Molar Volumes and Excess Isentropic Compressibilities of o-Toluidine + Tetrahydropyran with Pyridine or Benzene or Toluene Ternary Mixtures at 298.15, 303.15 and 308.15 K

The densities, ρ ₁₂₃, and speeds of sound, u ₁₂₃, of ternary o-toluidine (OT, 1) + tetrahydropyran (THP, 2) + pyridine (Py) or benzene or toluene (3) mixtures have been measured as a function of composition at 298.15, 303.15 and 308.15 K. Values of the excess molar volumes, $ V_{123}^{\text{E}} , $ and excess isentropic compressibilities, $ (\kappa_{\text{S}}^{\text{E}} )_{123} , $ of the studied mixtures have been determined by employing the measured experimental data. The observed thermodynamic properties were fitted with the Redlich–Kister equation to determine adjustable ternary parameters and standard deviations. The $ V_{123}^{\text{E}} $ and $ (\kappa_{\text{S}}^{\text{E}} )_{123} $ values were also analyzed in terms of Graph theory. It was observed that Graph theory correctly predicts the sign as well as magnitude of $ V_{123}^{\text{E}} $ and $ (\kappa_{\text{S}}^{\text{E}} )_{123} $ values of the investigated mixtures. Analysis of the data suggests strong interactions and a more close packed arrangement in OT (1) + THP (2) + Py (3) mixtures as compared to those of the OT (1) + THP (2) + benzene (3) or toluene (3) mixtures. This may be due to the presence of a nitrogen atom in Py which results in stronger interactions for the OT:THP molecular entity as compared to those with benzene or toluene.     

Excess Molar Volumes of Binary Mixtures of Hexanol and Polyethers at 25°C

Excess molar volumes V_m^E at 25°C and atmospheric pressure over the entire composition range for binary mixtures of 1-hexanol with n-polyethers: 2,5-dioxahexane, 3,6-dioxaoctane, 2,5,8-trioxanonane, 3,6,9-trioxaundecane, 5,8,11-trioxapentadecane, 2,5,8,11-tetraoxadodecane, and 2,5,8,11,14-pentaoxapentadecane are reported from densities measured with a vibrating-tube densimeter. Systems containing 2,5-dioxahexane, 2,5,8-trioxanonane, 2,5,8,11-tetraoxadodecane or 2,5,8,11,14-pentaoxapentadecane are characterized by V_m^E > 0, probably due to predominant positive contributions to V_m^E from the disruption of H bonds of 1-hexanol and to physical interactions. In contrast, mixtures with 3,6-dioxaoctane, 3,6,9-trioxaundecane, and 5,8,11-trioxapentadecane are characterized by V_m^E < 0, indicating that the negative contribution to V_m^E from interstitial accommodation is more important.     

Excess Molar Volumes of Ternary Mixtures of a Cyclic Ether with Aromatic Hydrocarbons at 308.15 K

Excess molar volumes, V_ijk^EV_{ijk}^{E}, are reported for ternary mixtures of tetrahydropyran (i)+benzene (j)+toluene or o- or p-xylenes (k) and tetrahydropyran (i)+toluene (j)+o- or p-xylenes (k) as a function of composition at 308.15 K. These V_ijk^EV_{ijk}^{E} values have been fitted to the Redlich–Kister equation to predict ternary adjustable parameters and standard deviations. The measured V_ijk^EV_{ijk}^{E} data have been analyzed in terms of Graph theory (which involves the topology of the constituents of mixtures). It has been observed that V_ijk^EV_{ijk}^{E} values predicted by Graph theory compare well with their corresponding experimental values.     

Excess Molar Enthalpies of Binary Mixtures of Trichloroethylene with Six 2-Alkanols at 25°C

Excess molar enthalpies H^E have been measured for the binary mixtures trichloroethylene + 2-propanol, + 2-butanol, + 2-pentanol, + 2-hexanol, + 2-heptanol, and + 2-octanol using an isothermal microcalorimeter at 25°C. All the mixtures present exothermic events and showed minimum negative H^E values around 0.50–0.60 mole fraction of trichloroethylene. Minimum values of H^E vary from 450 J-mol^-1 up to 530 J-mol^-1 depending on the molecular weight of alkanol. The results are explained in terms of the strong self-association exhibited by the 2-alkanols and the formation of aggregates between unlike molecules through O···HO hydrogen bonding. The experimental results for mixtures are well represented by the Redlich–Kister, NRTL, and Wilson equations, respectively.     

Excess Molar Volumes and Excess Partial Molar Volumes of Triethylene Glycol Monoethyl Ether–n-Alcohol Mixtures at 25°C

We have measured excess molar volumes V^E _m of binary mixtures of triethylene glycol monoethyl ether with methanol, ethanol, 1-propanol, 1-pentanol, and 1-hexanol over the full range of compositions at 25°C. The measurements were carried out with a continuous-dilution dilatometer. The excess molar volumes V^E _m are negative over the entire range of composition for the systems triethylene glycol monoethyl ether + methanol, + ethanol, and + 1-propanol and positive for the remaining systems, triethylene glycol monoethyl ether + 1-pentanol, and + 1-hexanol. The excess V^E _m increases in the positive direction with increasing chain length of the n-alcohol. The measured excess volumes have been compared to our previous published data with an effort to assess the effects of replacing methyl by ethyl groups and of inserting oxyethylene groups. The results have been used to estimate the excess partial molar volumes V^E _m,i of the components. The behavior of V^E _m and V^E _m,i with composition and the number of carbon atoms in the alcohol molecule is discussed.     

Excess Molar Volumes and Excess Partial Molar Volumes of Triethylene Glycol Monomethyl Ether–n-Alcohol Mixtures at 25°C

The excess molar volumes V ^E have been measured for binary mixtures of triethylene glycol monomethyl ether with methanol, ethanol, 1-propanol, 1-pentanol, and 1-hexanol as a function of composition using a continuous–dilution dilatometer at 25°C at atmosphere pressure. V ^E are negative over the entire range of composition for the systems triethylene glycol monomethyl ether + methanol, + ethanol, and + 1-propanol, and positive for the remaining systems, containing 1-pentanol and + 1-hexanol. V ^E increases in a positive direction with increasing carbon chain length of the n-alcohol. The excess partial molar volumes V _i ^E of the components were evaluated from the V ^E results. The behavior of V ^E and V _i ^E with composition and the number of carbon atoms in the alcohol molecule is discussed.     

Excess Molar Volumes and Viscosities for Binary Mixtures of 1-Alkoxypropan-2-ols with 1-Butanol, and 2-Butanol at 298.15 K and Atmospheric Pressure

Excess molar volumes Vm^E and kinematic viscosities v have been measured as a function of composition for binary mixtures of propylene glycol monomethyl ether （1-methoxy-2-propanol）, MeOCH2CH（OH）Me, propylene glycol monoethyl ether （1-ethoxy-2-propanol）, EtOCH2CH（OH）Me, propylene glycol monopropyl ether （1-propoxy-2-propanol）, PrOCH2CH（OH）Me, propylene glycol monobutyl ether （1-butoxy-2-propanol）, BuOCH2CH（OH）Me, and propylene glycol tert-butyl ether （1-tert-butoxy-2-propanol）, t-BuOCH2CH（OH）Me with 1-butanol, and 2-butanol, at 298.15 K and atmospheric pressure. The excess molar volumes are negative across the entire range of composition for all the systems with 1-butanol, and positive for the systems 2-butanol＋ 1-methoxy-2-propanol, and ＋1-propoxy-2-propanol, negative for the systems 2-butanol＋1-butoxy-2-propanol, and change sign for the systems 2-butanol＋ 1-ethoxy-2-propanol, and ＋ 1-tert-butoxy-2-propanol. From the experimental data, the deviation in dynamic viscosity η from ∑χiηi has been calculated. Both excess molar volumes and viscosity deviations have been correlated using a Redlich-Kister type polynomial equation by the method of least-squares for the estimation of the binary coefficients and the standard errors.     

A Study of Excess Molar Enthalpies and Excess Molar Volumes of Binary Mixtures of 1-Chloropentane + 1-Alkanol (from 1-Butanol to 1-Octanol) at 25°C.

Excess molar enthalpies H ^E _mand excess molar volumes V ^E _m at 25°Cand normal atmospheric pressure for the binary mixtures 1-chloropentane + 1-alkanol(from 1-butanol to 1-octanol) have been determined using a Calvet microcalorimeterand from density measurements using a vibrating tube densimeter. The H ^E _m valuesfor all the mixtures are positive and V ^E _m values are positive or negative dependingon the mole fraction of the chloroalkane. Experimental H ^E _m results are comparedwith the predictions of UNIFAC group-contribution models proposed by Dang andTassios and by Larsen et al., and are discussed in terms of molecular interactions.     

Excess Molar Volumes and Partial Molar Volumes of Dipropylene Glycol Monomethyl Ether + n-Alkanol Mixtures at 25°C

The excess molar volumes V^E for binary liquid mixtures containing dipropylene glycol monomethyl ether and methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, and 1-heptanol have been measured using a continuous dilution dilatometer over the whole mole fraction range at 25°C at atmospheric pressure. V^E are negative over the whole composition range except for the systems containing 1-pentanol, 1-hexanol, or 1-heptanol which are positve at every composition. V^E increases in a positive direction with increase in chain length of the n-alcohol. The results have been used to estimate the excess partial molar volumes V_i^E of the components. The change of V^E and V_i^E with composition and the number of carbon atoms in the alcohol molecule are discussed as a basis to understand some of the molecular interactions present in the mixtures:     

Excess Molar Volumes and Viscosities of Binary Mixtures of Methanol and the Ionic Liquid 4-Methyl-N-butylpyridinium Tetrafluoroborate at 25, 40, and 50°C

Experimental data of densities and viscosities are presented for the system 4-methyl-N-butylpyridinium tetrafluoroborate + methanol at 25, 40, and 50, 323.15 K and ambient pressure using a vibratage-tube densimeter and an Ubbelohde viscometer. Excess molar volumes V ^E and excess logarithm viscosities (ln )^E have been determined. V ^E is negative and (ln )^E positive over the entire mixture composition.     

Excess Volumes,Isentropic Compressibilities and Viscosities for Binary Mixtures of <Emphasis Type="Italic">tert</Emphasis>-Butylamine with Alkyl Acetates at 303.15 K

The data on excess volume (V ^E), density (ρ), viscosity (η) and speeds of sound (u) for the binary mixtures of tert-butylamine (TBA) + methyl acetate (MA), + ethyl acetate (EA), + butyl acetate (BA) and + isoamyl acetate (IAA) at 303.15 K were measured experimentally over the entire range of composition. Speeds of sound were evaluated using Jacobson’s free length theory (FLT) and Schaaffs’ collision factor theory (CFT). The viscosity data were analyzed on the basis of the corresponding states approach and the Grunberg and Nissan treatment. The experimental results for excess volume, deviation in isentropic compressibility and deviation in viscosity were discussed in terms of molecular interactions between unlike molecules. A Redlich-Kister type equation was used to fit the experimental data on excess volume, deviation in compressibility and deviation in viscosity.     

Excess Chemical Potentials, Excess Partial Molar Enthalpies, Entropies, Volumes, and Isobaric Thermal Expansivities of Aqueous Glycerol at 25°C

The vapor pressures p the excess partial molar enthalpies of glycerol H _Gly ^E the densities d and the thermal expansivities _p of aqueous glycerol were measured at 25°C. From the vapor pressure data, the excess chemical potential of H₂O µ _W ^E was calculated, assuming that the partial pressure of glycerol p _Gly is negligibly small. The excess chemical potential of glycerol µ _Gly ^E was estimated by applying the Gibbs–Duhem relation and these data were used to calculate the excess partial molar entropies S _Gly ^E . From the density data, the excess partial molar volumes of glycerol V _Gly ^E and from the thermal expansivity data, the normalized cross fluctuations ^SV, introduced by us earlier, were evaluated. While the detailed manner in which glycerol modifies the molecular arrangement of H₂O in its immediate vicinity is yet to be elucidated, the hydrogen bond probability in the bulk H₂O away from solute molecules is reduced gradually as the glycerol composition increases to the point where putative presence of icelike patches is no longer possible. Thereupon, a qualitatively different mixing scheme seems to set in.     

Volumetric, Ultrasonic and Transport Properties of Binary Liquid Mixtures Containing Dimethyl Formamide at 303.15 K

Excess volumes （v^E）, ultrasonic velocities （u）, isentropic compressibility （△Ks） and viscosities （η） for the binary mixtures of dimethyl formamide （DMF） with 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,2,4-trichlorobenzene, o-chlorotoluene, m-chlorotoluene, p-chlorotoluene, o-nitrotoluene and m-nitrotoluene at 303.15 K were studied. Excess volume data exhibit an inversion in sign for the mixtures of dimethyl formamide with 1,2- and 1,3-dichlorobenzenes and the property is completely positive over the entire composition range for the mixtures of dimethyl formamide with 1,2,4-trichlorobenzene, o-nitrotoluene and m-nitrotoluene. On the other hand, the quantity is negative for the mixtures of dimethyl formamide with chlorotoluenes. Isentropic compressibility （Ks） has been computed for the same systems from precise sound velocity and density data. Further, deviation of isentropic com- pressibility （△Ks） from ideal behavior was also calculated. AKs values are negative over the entire volume fraction range in all the binary mixtures. The experimental sound velocity data were analysed in terms of Free Length Theory （FLT） and Collision Factor Theory （CFT）. The viscosity data were analysed on the basis of corresponding state approach. The measured data were discussed on the basis of intermolecular interactions between unlike molecules.     

Measurement and Correlation of Excess Molar Enthalpy of Binary Mixtures Containing Butyl Acetate + 1-Alkanols (C1–C6) at 298.15 K

Excess molar enthalpies, ?H _m ^E , for the binary mixtures of butyl acetate + 1-alkanols, namely (methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, and 1-hexanol), were measured over the whole range of composition at 298.15 K using a Parr 1455 solution calorimeter. The excess partial molar enthalpies, ?H _m,i ^E , were calculated from the experimental excess molar enthalpies using the Redlich–Kister polynomial equation. The sign of ?H _m ^E for all systems are positive because of the disruption of hydrogen bonding and dipole–dipole interactions in the alkanols and esters, respectively. The magnitude of the ?H _m ^E values increases with increasing alkyl chain length. The behavior of ?H _m ^E was analyzed in terms of the length of the alkanol chain, the nature and type of intermolecular interactions and the balance between positive and negative effects on deviations from ideality. The experimental excess molar enthalpy data have also been correlated using the Redlich–Kister and SSF equations and two local composition models (UNIQUAC and NRTL).     

Partial Molar Volumes of Glycine and dl-Alanine in Aqueous Ammonium Sulfate Solutions at 278.15, 288.15, 298.15 and 308.15 K

In this work, the partial molar volumes of glycine and dl-alanine in aqueous solutions of ammonium sulfate at 0.0, 0.1, 0.3, 0.7, and 1.0 mol·kg^?1 are determined between 278.15 and 308.15 K. Transfer volumes were obtained, which are larger for glycine than dl-alanine. On the contrary, the hydration numbers are higher for dl-alanine than glycine, and dehydration of the amino acids is observed with increasing temperature or salt molality. The data suggest that interactions between ion and charged/hydrophilic groups are predominant and, by applying the methodology proposed by Friedman and Krishnan, it was concluded that they are mainly pairwise. A group-contribution scheme has been successfully applied to the pairwise volumetric interaction coefficient. Finally, the dehydration effect on glycine, alanine and serine in the presence of different electrolytes has been rationalized in terms of the charge density and a parameter accounting for the cation’s hydration.     

Excess Molar Volumes for Binary Mixtures of 1-Alkanol and 1-Alkene. III. The System 1-Hexanol + 1-Alkene at 25°C

Excess molar volumes, V ^E, are reported for binary mixtures of 1-hexanol with the homologous C₆, C₇, C₈, and C₁₀ 1-alkenes at 25°C. In this series of mixtures, the V ^E values vary as a function of mole fraction from positive–negative sigmoid shaped curves exhibiting a very small positive lobe in the dilute alkanol region for the shortest chain 1-alkene to positive values over the whole concentration range for the longer chain 1-alkene. The partial molar excess volumes, V _i ^E, were calculated for the components over the whole concentration range. The partial molar volume of 1-hexanol in the 1-hexene system shows a large and sharp minimum and in the 1-decene system is positive over the whole concentration range. The modified model [Treszczanowicz et al., J. Solution Chem. 31, 455 (2002) originally proposed by Treszczanowicz and Benson Fluid Phase Equilibr. 23, 117 (1985)] was used for the interpretation and prediction of the reported data. The model describes qualitatively the variation of V ^E with the length of the molecule and concentration as a result of superposition of the contributions of association, free volume, and nonspecific interactions.     

Theoretical Description of Excess Molar Functions in the Case of Very Small Excess Values. Investigation of Excess Molar Volumes of Propan-2-ol + Alkanol Mixtures

The densities of propan-2-ol + pentan-1-ol, + hexan-1-ol, + heptan-1-ol, + octan-1-ol + nonan-1-ol and speeds of sound in propan-2-ol + pentan-1-ol, + heptan-1-ol, + nonan-1-ol have been measured over the whole composition range at 298.15 K. Excess molar functions determined from the experimental data have been plotted as functions of composition. The excess molar volumes have been interpreted on the basis of the Symmetrical Extended Real Associated Solution Model (S-ERAS).