Specific interactions including imidazolium andN-methylimidazolium lons. I. Interactions with the picrate anion

The conductances of solutions of methylimidazolium and imidazolium picrate (MeImHPic and ImHPic) in nitrobenzene-benzene mixtures (27.2–. These triple ions are highly stabilized by the hydrogen bond between the second NH group of the ion pair and the second picrate ion. Values of the formation constants for the ion pair ImHPic and for the triple ion PicImHPic^– have been calculated and are discussed.     

Relative permittivity of the binary mixtures of 2-methoxyethanol with diethylene glycol,triethylene glycol,tetraethylene glycol,and polyethylene glycol 200 at various temperatures

Relative permittivities at T = (293.15, 298.15, and 303.15) K in the binary liquid mixtures of 2-methoxyethanol with diethylene glycol, triethylene glycol, tetraethylene glycol, and polyethylene glycol 200 have been measured over the entire mixture compositions. The relative permittivity deviations (Δε) were calculated from these experimental data. The results are discussed in terms of intermolecular interactions and structure of studied binary mixtures.     

Excess molar volumes and deviations of the relative permittivity of the binary mixtures of 2-propoxyethanol with diethylene,triethylene, and tetraethylene glycols at various temperatures

Densities and relative permittivities at T = (293.15, 298.15, and 303.15) K in the binary liquid mixtures of 2-propoxyethanol with diethylene glycol, triethylene glycol, and tetraethylene glycol have been measured over the entire mixture compositions. These data have been used to compute the excess molar volumes and deviations of the relative permittivity. The results are discussed in terms of intermolecular interactions in the bulk of studied the binary mixtures.     

Effect of tetrahydrofuran on the conductance and ion-pairing of hydrogen chloride in wet and dry methanol mixtures

The molar conductance of dilute solutions of HCl in wet (68.5% methanol + 31.5% tetrahydrofurane mixtures at 25°C have been measured. The data were analyzed using the Fuoss-Hsia equation to calculate the infinite dilution molar conductances and association constants. The trend of the limiting conductances in these mixtures as a function of the water content shows, once more, the peculiar minimum due to the anomalous proton conductance mechanism. From these data the limiting molar conductance in the anhydrous binary solvent system was evaluated. The percentage excess proton mobility with respect to potassium ion has also been determined. All these data are compared to those found in a binary isodielectric methanol mixture containing as cosolvent 1,4-dioxane. This comparison shows that proton mobilities are very similar in both solvent mixtures. The dielectric constants, refractive indices, viscosities and densities of the methanol-tetrahydrofuran mixtures in the whole mole fraction range have been measured and are reported. An analysis of the excess molar volumes and viscosities shows a slight deviation of this system from ideality.     

Representation of Electrical Conductances for Polyvalent Electrolytes by the Quint-Viallard Conductivity Equation. Universal Curves of Limiting Conductances and Walden Products of Electrolytes in Mixed Solvents. Part 5. Symmetrical 2:2, 3:3 and Unsymmetrical 1:2, 2:1 and 1:3 Type Electrolytes

Conductivities of symmetrical and unsymmetrical electrolytes of 2:2, 3:3, 1:2, 2:1 and 1:3 types in ethanol–water and the 1,4-dioxane–water mixtures were analyzed using the Quint-Viallard conductivity equation and taking into account the ion association effect. The molar limiting conductances and the ion association constants were reexamined for various multivalent electrolytes. One non-aqueous system, methanol–ethylene glycol mixtures, was also considered. The limiting conductances were also examined in the framework of universal curves of limiting conductances and the excess Walden products introduced by the author. These new concepts in the analysis of conductance data allow the estimation of values of limiting conductances of electrolytes or ions, to give an indication about the quality of the conductivity measurements and the type of interactions expected in the systems. It was found that for any type of electrolyte only one universal curve of limiting conductances exists. In the water-rich mixtures, attractive interactions (structure-making effects) are expected when electrolytes are added to mixtures with ethanol or with 1,4-dioxane. In contrast, in ethylene glycol–methanol-rich mixtures repulsive interactions (structure-breaking effects) are more likely.     

Densities and relative permittivities for mixtures of 2-methoxyethanol with DEA and TEA, at various temperatures

Densities () and relative permittivities () of numerous binary mixtures of 2-methoxyethanol (ME) (1)+diethylamine (DEA) (2) at four temperatures and 2-methoxyethanol (1)+triethylamine (TEA) (2) at five temperatures, between (291.15 and 313.15) K, are reported. These results are used to calculate excess molar volumes, and deviations in the relative permittivities. The results are fitted to the Redlich-Kister polynomial equation to estimate the binary coefficients and standard errors. Furthermore, the experimental results are used to disclose the nature of binary interactions in the bulk of studied the binary mixtures.This revised version was published online in November 2005 with corrections to the Cover Date.     

The effect of keto-enol tautomerism on the properties of methylethylketone + benzene mixtures

Ratkovics, F. and Palágyi-Fényes, B., 1984. The effect of keto-enol tautomerism on the properties of methylethylketone + benzene mixtures. Fluid Phase Equilibria, 16: 99–116.The density, viscosity, static relative permittivity, conductivity and refractive index of methylethylketone + benzene mixtures have been measured in the interval 293.15–313.15 K. Vapor-liquid equilibrium data for the same mixtures were measured between 313.15 and 333.15 K. The results obtained indicate the formation of an association complex between benzene and methylethylketone in the enolic form, and the keto-enol equilibrium is shifted accordingly towards formation of the latter. Electrolytic dissociation of the benzene-enol association complex contributes to the conductivity of the benzene-ketone mixtures. In addition to concentration, the relative permittivity also has a considerable influence on the conductivity, since a considerable number of nondissociated ion pairs are formed (in the sense of Bjerrum theory). Comparison of the model based on the physical picture outlined and the experimental results indicates that ions deriving from the benzene-enol association complex are solvated in the region of higher benzene molar ratios. The model is also suitable for the interpretation of results obtained for mixtures containing other ketones and proton acceptors.     

Measurements of densities,viscosities, speeds of sound and relative permittivities and excess molar volumes,excess isentropic compressibilities and deviations in relative permittivities and molar polarizations for dibutyl ether + benzene, + toluene and + p-xylene at different temperatures

The densities ρ, dynamic viscosities η, speeds of sound u, and relative permittivities ε_r, for (dibutyl ether + benzene, or toluene, or p-xylene) have been measured at different temperatures over the whole composition range and at atmospheric pressure. The mixture viscosities have been correlated with semi empirical equations. Calculations of the speed of sound based on Nomoto’s equation have been found to be close to experimental values for the three mixtures and at two temperatures. Excess functions such as excess molar volumes V_m^E, excess isentropic compressibilities κ_s^E, deviations in relative permittivities δε_r, and molar polarizations δP_m were calculated and fitted to Redlich–Kister type equations.     

Association of Ionic Liquids in Solution: Conductivity Studies of [BMIM][Cl] and [BMIM][PF6] in Binary Mixtures of Acetonitrile + Methanol

The concentration dependence of molar conductance for 1-butyl-3-methylimidazolium chloride and 1-butyl-3-methylimidazolium hexafluorophosphate in binary mixtures of acetonitrile + methanol was investigated to explore the ion association behavior of imidazolium based ionic liquids. The limiting molar conductance $(\Uplambda_{m}^{0})$ ( Λ m 0 ) , association constants (K _a ⁰ ) and the maximal distance between the oppositely charged ions in ion pairs (R _ij ) in the mixed solvent mixtures were evaluated following the framework of Barthel’s low-concentration chemical model. The investigated ILs display opposing trends in ion association behavior with change in solvent composition of acetonitrile + methanol binary mixtures. The results are discussed in light of ionic liquid and solvent specific ion?solvent and ion?ion interactions in the mixed solvent systems.     

Ion pairing in solutions of sodium tetraphenylborate

Conductance data are presented for sodium tetraphenylborate (NaBPh₄) in three solvent systems: water-dimethyl sulfoxide, water-acetone, and acetone-dimethyl sulfoxide. These and other data from the literature were first analyzed by the three-parameter equation Λ^′=Λ₀+Aτ²+Bτ³, where $$\Lambda \prime = [\Lambda (obs.) + \beta _0 c^{1/2} (1 + 0.5\tau ln 2\tau )]/[1 - \alpha _0 c^{1/2} + (\tau ^2 /3) ln 2\tau ]$$ Here, β₀ is the Onsager electrophoresis coefficient, α_oc^1/2 the limiting relaxation term, τ=e²κ/2DkT, κ^?1 is the Debye-Hückel distance, andA andB are empirical constants. The fact that three parameters are necessary to reproduce the data shows that ion pairing is not negligible for NaBPh₄ solutions despite the fact that the conductance curve lies above the limiting tangent even in ethanol (D=24.30). The quantity Λ_o is the limit of Λ^′ at zero concentration; the sum Aτ²+Bτ³ represents the part of the observed conductance from which the pairing constantK _Λ and the distance parameterR are derived. Conductance experiments should therefore be designed so that this sum is as large as possible, subject to the restriction that the highest concentration should not exceed 10^?7D³ (where the effects of short-range three-ion interactions are no longer negligible). Pairing constants for NaBPh₄ in the various solvents range from 4.6 in water to 70 in a mixture of Me₂SO and Me₂CO with dielectric constantD=23.80. The dependence ofE _s (the difference in free energy between solvent-separated pairs and contact pairs) on solvent composition is different for aprotic solvents and for mixtures containing water; for the latter, theE _s/kT vs. l/D plot shows a maximum while for the former the curve is monotone descending. The Walden produces (Λ_oη=limiting conductance times viscosity) plotted againstD ^?1 follow the same pattern.     

Conductance of lithium,sodium and potassium nitrates in acetonitrile-water and ethanol-water isodielectric mixtures at 25°C

Precise conductance measurements of solutions of lithium, sodium and potassium nitrates were made at 25°C in acetonitrile-water and ethanol-water isodielectric mixtures, containing up to 15 mole percent organic-solvent, and the data analyzed by the 1978–80 Fuoss conductance equations. Single ion conductances were determined with the help of transference numbers in the case of ethanol-water mixtures. Ion-pair association constants are discussed in terms of contact and solvent-separated ion-pairs and were found to be almost equal to those for the halides. The anion appears more sensitive than the cations to the solvent structure in mixtures rich in water.     

The temperature coefficient of conductance for the alkali metal,halide, tetraalkylammonium,halate, and perhalate ions in D2O

Precise limiting ionic conductance data are reported for the first time for the alkali metal and tetraalkylammonium ions in D₂O at 10°C as well as similar data for the halate and perhalate ions in D₂O and H₂O at 10 and 25°C. Precise transference numbers by the moving-boundary method are also reported for KBr in D₂O at 10°C and, as a check on earlier work, for KCl in D₂O at 25°C. In general, the structural properties of the ions, as reflected in the temperature coefficient of the limiting ionic conductances, are enhanced in D₂O compared to H₂O, although the differences are often small.     

Heteromolecular structures in aqueous solutions of dimethylformamide and tetrahydrofuran,according to molecular dynamics data

The complex dielectric permittivity of aqueous solutions of tetrahydrofuran and dimethylformamide in wide ranges of temperature (220–300 K) and pressure (0.1–12 MPa) is studied by means of molecular dynamics. The autocorrelation functions of the dipole moments of molecules are calculated. Dielectric permittivity spectra are obtained. The dielectric relaxation times are determined as functions of the tetrahydrofuran and dimethylformamide concentrations in the indicated binary mixtures. The dielectric relaxation frequency shifts toward low frequencies in the range of tetrahydrofuran and dimethylformamide concentrations x ≤ 0.5 molar fraction, due to the formation of heteromolecular structures with hydrogen bonds. This is confirmed by the negative values of the excess dielectric permittivities of binary solutions at x ～ 0.3–0.4 molar fraction.     

Relative permittivities and refractive indices of binary mixtures of cyclohexanone with dichloromethane,trichloromethane, 1,2-dichloroethane,trichloroethene and cyclohexane at T=303.15 K

Relative permittivities, ϵ_r, and refractive indices, n_D, have been measured for binary liquid mixtures of cyclohexanone (C₆H₁₀O) with dichloromethane (CH₂Cl₂), trichloromethane (CHCl₃), 1,2-dichloroethane (CH₂ClCH₂Cl), trichloroethene (CHClCCl₂), and cyclohexane (c-C₆H₁₂) at T=303.15 K. The values of the deviations of ϵ_r and n_D from values arising from mole fraction average, which are represented respectively by Δϵ_r and Δn_D have been calculated. Values of ϵ_r and Δn_D have been fitted by the method of least squares to smoothing equations. Δϵ_r for the various mixtures has been discussed from the viewpoint of the existence of specific interactions between the components.     

Electrical conductances of tetrabutylammonium bromide and tetrapentylammonium bromide in 2-ethoxyethanol + water mixtures at 308.15, 313.15, 318.15 and 323.15 K

The electrical conductances of the solutions of tetrabutylammonium bromide (Bu₄NBr), and tetrapentylammonium bromide (Pen₄NBr) in 2-ethoxyethanol (1) + water (2) mixed solvent media containing 0.25, 50 and 0.75 mass fractions of 2-ethoxyethanol (w ₁) have been reported at 308.15, 313.15, 318.15 and 323.15 K. The conductance data have been analyzed by the 1978 Fuoss conductance–concentration equation in terms of the limiting molar conductance (Λ⁰), the association constant (K _A) and the association diameter (R). These two electrolytes are found to exist essentially as free ions in the solvent mixtures with w ₁ = 0.25 and 0.50 over the entire temperature range; however, slight ionic association was observed in the mixed solvent medium richest in 2-ethoxyethanol. The electrostatic ion–solvent interaction is found to be very weak for the tetraalkylammonium ions in the aqueous 2-ethoxyethanol mixtures investigated.     

Temperature dependence of electric conductivity of molten binary mixtures of alkali and rare-earth metals chlorides

The temperature dependences of the specific and molar electric conductances of CeCl₃-MCl and LnCl₃-KCl (M=Li, Na, K, and Cs; Ln=Er and Yb) molten binary mixtures of various compositions were studied. The size of the cations of alkali and rare-earth metals was demonstrated to affect the intensity of the interactions of the components of the systems. Deviations of the molar conductance isotherms from additivity and dependence of the isotherms on the ratio between the mixture components were explained by the formation of complexes in the melts.     

Density and relative permittivity of (pyridine + 2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol,and 2-butoxyethanol) binary mixtures at 298.15 K

The densities and relative permittivities of binary mixtures of pyridine with 2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol and 2-butoxyethanol have been measured as a function of composition, at T = 298.15 K. From the experimental data the excess molar volume (V^E) and the deviation in the relative permittivity (Δε) from a mole fraction average have been calculated. The results are discussed in terms of intermolecular interactions and structure of studied binary mixtures.     

Analytical Methods for Determining the Concentration Ratio in Mixtures of Trioctylphosphine Oxide and Di(2-Ethylhexyl)Phosphoric Acid

Abstract

Analytical methods are described for determining the concentration ratio of trioctylphosphine oxide (TOPO) and di(2-ethylhexyl)phosphoric acid (D₂ EHPA) in hydrocarbon solvents or in mixtures where the D₂ EHPA is the solvent. The Electron Spectroscopy for Chemical Analysis (ESCA) method was used to analyze the mixtures for the relative amounts of phosphine oxide-phosphorus to phosphoric acid-phosphorus as well as the variance with the mixture composition of the Ols/P2p signal intensity. The nmr signal strength of the protons of the oxymethylene group of the D₂ EHPA and the signal strength of the other protons of D₂ EHPA and TOPO were measured in solutions of varying concentrations of D₂ EHPA and TOPO. Mass spectral comparisons of the molecular ion strengths of TOPO and D₂ EHPA were also correlated with mixture composition.     

Influence of the dielectric constant on ion-pair and ion-ligand complex formation

The effect of dielectric constant on ion association of triethylammonium picrate and methylimidazolium picrate and on ion-ligand complex formation between the cations Et₃NH⁺ and MeImH⁺ and 1-methylimidazole was investigated from conductance data carried out in nitrobenzene-benzene mixtures (34.8K _A satisfy in first approximation the relation logK _A 1/D. The center-to-center distance å has been calculated and compared to the value obtained for nonhydrogenbonded ion pairs. The ion-ligand association constantK ₁ ⁺ increases as the dielectric constant of the medium decreases. Plots of logK ₁ ⁺ against 1/D give straight lines, the slopes of which are consistent with the predictions of a theory that interprets the effect of the dielectric constant in terms of changes in the polarization energy of the solvent around the complexed and the uncomplexed ions. For these interactions, the complexed ions can be approximated as charged spheres, the volume of which is equal to that of the bare ion plus the volume of the ligand.     

Studies on the effect of ethanol on the solvation behaviour of thiamine hydrochloride in water

The specific conductance of Thiamine hydrochloride in water and water-ethanol mixtures was measured at different temperatures 283, 293, 303 and 313 K. Kraus-Bray and Shedlovsky models of conductivity were used for analyzing conductance data. The limiting molar conductance, association constant K _a, energy of activation of the rate process E _a, and related thermodynamic parameters have been determined. Based on viscosity of the solvent, Walden product and Stokes molecular radius were also been determined. Born model of ion solvation was proved. Standard thermodynamic parameters of association (G _a, H _a and S _a) were calculated and discussed. The results show the decrease in limiting molar conductance and increase in K _a with decrease in relative permittivity. Such computed values have been used to discuss the solvation behaviour of Thiamine hydrochloride in water-ethanol mixtures.