Conductance of 1∶1 electrolytes in methyl acetate

The electrolytic conductances of NaClO₄, NaB(C₆H₅)₄, (n-C₄H₉)₄NClO₄ and (n-C₄H₉)₄NPF₆ have been measured in methyl acetate at 25°C. A dominating feature of these electrolyte solutions is, as expected, strong ion pairing. In addition it is found that the formation of triple ions makes an important contribution to the overall molar conductivities. The data suggest that there are strong ion-solvent interactions leading to structure-enhanced (after Diamond) ion association and triple ion formation which has an exact analogy in the phenomena of salting-in. The effects of increasing solution permittivity and viscosity are discussed, particularly in regard to comparing two models of treating conductivity data. The first model includes ion pairs and triple ions, and the second model ignores triple ion formation ascribing the anomalous increase in molar conductivities to a decrease in the ion association equilibrium constant caused by increasing solution permittivity.     

Ion association and solvation behavior of tetraalkylammonium iodides in binary mixtures of dichloromethane + N,N-dimethylformamide probed by a conductometric study

Precise measurements on electrical conductances of tetraalkylammonium iodides, R(4)NI (R = n-butyl to n-heptyl), in different mass% (0-100) of dichloromethane (DCM) + N,N-dimethylformamide (DMF) at 298.15 K have been performed. Limiting molar conductances (Λ(0)), association constants (K(A)) and co-sphere diameter (R) for ion-pair formation in the mixed solvent mixtures have been evaluated using the Fuoss conductance-concentration equation. However, the deviation of the conductometric curves (Λ versus √c) from linearity for the electrolytes in 100 mass% of DCM indicated triple ion formation, and therefore corresponding conductance data have been analyzed by the Fuoss-Kraus theory of triple ions. Limiting ionic molar conductances λ have been calculated by the reference electrolyte method along with a numerical evaluation of ion pair and triple ion formation constants (K(P)≈K(A) and K(T)). The results have been interpreted in terms of ion-solvent interactions and structural changes in the mixed solvents.     

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.     

Ion association of lithium bromide,chloride and picrate and of sodium picrate in 2-propanol at 25°C. I. Conductance measurements

The molar conductances of lithium bromide, chloride and picrate, and of sodium picrate have been determined as a function of salt concentration in 2-propanol solvent at 25°C. Values of the limiting molar conductance, Λ₀, and ion pair formation constant K_A have been calculated for each of these salts using both the Fuoss 1978 and the Lee and Wheaton conductance equations. Both of these equations yield comparable results for the present systems. The limiting conductances found here are compored with those reported for lithium chloride in 1-propanol and acetone and with those for the picrates in acetone and 2-butanone, all solvents of comparable dielectric constants. The Rasaiah-Friedman square mound potential, h_+?/kT, has been calculated for each salt using the approach of Justice and Justice. These values for 2-propanol have been compared with those for lithium chloride in 1-propanol and in acetone and for the picrates in acetone and 2-butanone.     

Thermodynamic dissociation constants of salicylic and monochloroacetic acids in mixed solvent systems from conductance measurements at 25°C

The molar conductances of dilute solutions of salicylic and monochloroacetic acids in binary mixtures of methanol, ethanol, 1-propanol, N,N-dimethylformamide, acetone, acetonitrile, tetrahydrofuran and dioxane with water have been measured at 25°C. The Lee-Wheaton conductance equation was fitted to the data in order to derive thermodynamic dissociation constants and limiting molar conductances. The results were compared with those in the literature pertaining to analogous media, mostly derived potentiometrically. The findings are interpreted in terms of a solvent effect on the ionization of these acids in mixed solvent systems.This paper is dedicated to the late Professor Raymond M. Fuoss on his 3^rd anniversary.     

Association of carboxylic acids in aqueous solutions from conductivity data

Using precision conductivity data for aqueous carboxylic acid systems at 25 and 30°C, accurate thermodynamic ion association and dimerization equilibrium constants were determined. The data for formic, acetic, propionic and butyric acids are analyzed with the Fuoss-Hsia conductance equation as modified by Justice and Barthel. The treatment requires that triple ion formation is negligible.     

Conductance of substituted amine perchlorates and picrates in N-methyl-2-pyrrolidinone at 25°C

Conductance measurements of 16 perchlorates and picrates of substituted ammonium cations have been made in N-methyl-2-pyrrolidinone (NM-2-Py) at 25°C. To aid in the estimation of ionic conductances, measurements of tetrabutyl-ammonium tetraphenylborate were also included. The data were analyzed by both the full Pitts equation and the expanded Pitts equation in order to obtain limiting molar conductances _o and the ion association constants K _A . The results showed that pyridinium perchlorate and piperidinium, 2,4-dimethyl-pyridinium, 2,4,6-trimethylpyridinium picrates and tetrabutylammonium tetraphenylborate appear to be completely dissociated in NM-2-Py. The values of K _A for the other salts range from 1 to 36 dm³-mol^–1. Limiting molar conductances for the cation were based on the Coplan-Fuoss assumption.On leave 1973–1975 from University of Gdask, Poland.     

混合电解质的电导测定

电导测定为研究离子与离子之间的缔合效应、离子与溶剂的相互作用及溶剂结构提供了一个有效手段 .目前 ,电解质水溶液、电解质非水溶剂体系的电导数据却很缺乏 ,而混合电解质体系的电导测定在理论及应用方面都很重要 .作为全面系统地考察金属氯化物的混合电解质的电导性质变化规律 ,前文已测定了 Na Cl- KCl- H2 O体系 [1] 、 Na Cl- Rb Cl- H2 O体系及 KCl- Rb Cl- H2 O体系的电导值 [2 ] ,本文用自行设计的电导池测定了 Ca Cl2 - H2 O,Ca Cl2 - Na Cl- H2 O,Ca Cl2 - KCl- H2 O体系在 2 98.1 5 K时的低浓度电导数据 ,探讨了…     

PrOH-H2O混合溶剂中LiCl,NaCl的电导研究

本文设计并制作一套可搅拌U型电导池, 并用其测定了LiCl, NaCl在PrOH-H2O二元混合溶剂中的摩尔电导。应用Fuoss-Onsager电导方程关联得到Λ。, a°及Ka, 并据此探讨了LiCl, NaCl-PrOH-H2O的微观结构及相互作用。     

Measurements of vapour-liquid equilibria,densities, viscosities and dielectric properties of cyclohexanone + triethylamine mixtures with respect to keto-enol tautomerism

Densities, ?, kinematic viscosities ν, refractive indices n_D referred to the sodium D-line, static relative permittivities ε, specific conductances κ and vapour-liquid equilibrium data for cyclohexanone + triethylamine mixtures have been determined at two temperatures. Excess properties of mixing calculated from these data indicate that in such mixtures considerable amounts of enol-amine associates are formed. The permittivity data indicate that the formation of associates is an exothermic process, which also has a marked influence on the thermodynamic excess properties of the mixtures. The enol-amine associates may undergo electrolytic dissociation. A common evaluation of static relative permittivities and specific conductances shows that for the mixture the conductance data are affected considerably by the formation of undissociated ion pairs in the sense of Bjerrum theory, especially at concentrations of the mixture where it is less polar. The conductance data are also influenced considerably by the fact that the ion pairs are solvated if the molar ratio of triethylamine exceeds 0.5.     

Electrical conductance,density and viscosity of the system lead(II) dodecanoate/dodecanoic acid

Data are presented for the densities, electrical conductances and viscosities of the molten system lead(II) dodecanoate/dodecanoic acid. Over the concentration range studied, molar volumes are linear functions of concentration at any selected temperature, although there are indications of deviations from ideal behaviour over the complete composition range from pure soap to pure acid. The molar volumes of the system lead(II) carboxylate/carboxylic acid for the even chain acids C₁₀ to C₁₈ are linear functions of chain length. As with other lead(II) dodecanoate systems, the Arrhenius plots for the conductance of the mixtures show curvature.Activation energies for conductance in the low temperature region show a steady decrease with increasing mole fraction of the acid. It is suggested that this arises largely from the increased mobility of the Pb²⁺ ion. The activation energies for viscous flow in the mixtures are similar to that of pure lead dodecanoate. Studies of the viscosities of the system lead(II) carboxylate/carboxylic acid as a function of the temperature for the even chain length acids C₁₀ to C₁₈ suggest a slight decrease in size of the unit of viscous flow when acid is present.     

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.     

Representation of Electrical Conductances for Polyvalent Electrolytes by the Quint-Viallard Conductivity Equation. Part 4. Symmetrical 2:2, 3:3 and Unsymmetrical 2:1, 3:1 and 1:3 Type Electrolytes in Pure Organic Solvents

Conductivities of symmetrical and unsymmetrical electrolytes of 2:2, 3:3, 2:1, 3:1 and 1:3 charge types in pure organic solvents (methanol, ethanol, 1-propanol, dimethyl sulfoxide, acetonitrile, formamide, N-methylformamide, N,N-dimethylformamide, N-methylacetamide and N,N-dimethylacetamide) 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 determined for various multivalent electrolytes in these solvents using the literature conductivities. In many cases, for the first time, it was possible to obtain consistent values of the limiting ionic conductances in organic solvents.     

NaCl(或KCl)-CH3OH-H2O体系的摩尔电导

CHaOH－HzO体系具有非常特殊的性质，同时在工业生产及临床治疗方面有着十分广泛的应用，文献中有大量地从不同角度就这类体系进行研究的报道．然而，就N3CI及KCI－CH30H－H20体系的电导研究而言，文献中仅有关干KCI－CH30H－H20（间隔20％CH30H）的部分研究工作．作为全面、系     

The association of aromatic anions in water

Molar conductances of dilute solutions of sodium 2-naphthalenesulfonate at 25°C and of sodium 2-anthraquinonesulfonate have been measured at 25 and 37°C. These data are interpreted to show that the anthraquinonesulfonate anion is dimerized in solution. Dimerization constants and the enthalpy and entropy of dimerization are calculated. Spectrophotometric absorbancies have been measured at 25, 30, 35 and 40°C for a series of aqueous solutions containing both sodium 4-dimethylaminobenzenesulfonate and sodium 3-nitrobenzenesulfonate. Equilibrium constants and enthalpy and entropy changes for formation of the 1 1 complex between these two ions have been calculated from these data. The formation of these complexes between like-charged ions, and of dimers of other aromatic solutes in water is discussed in terms of a two-state model of hydrophobic hydration.     

氨基酸在水或氯化钾水溶液中体积性质的研究

在298.15K和常压下利用密度法测定了十几种α-氨基酸在水或氯化钾水溶液中的表观摩尔体积, 由此得到了各氨基酸的偏摩尔体积和其相应的转移偏摩尔体积,以及氨基酸中侧链对其偏摩尔体积的贡献值。从理论上计算了各氨基酸在上述溶液浓度的增加而增大; 氨基酸共溶质间的相互作用以1:1形式为主; 氨基酸的水化数随盐浓度的增加而减小。对所得结果进行了定性讨论。     

Interactions of some amino acids and glycine peptides with aqueous sodium dodecyl sulfate and cetyltrimethylammonium bromide at T=298.15 K: a volumetric approach

The apparent molar volumes V_φ of glycine, alanine, valine, leucine, and lysine have been determined in aqueous solutions of 0.05, 0.5, 1.0 mol · kg⁻¹ sodium dodecyl sulfate (SDS) and 1.0 mol · kg⁻¹ cetyltrimethylammonium bromide (CTAB) by density measurements at T=298.15 K. The apparent molar volumes have also been determined for diglycine and triglycine in 1 mol · kg⁻¹ SDS and CTAB solutions. These data have been used to calculate the infinite dilution apparent molar volumes V₂⁰ for the amino acids and peptides in aqueous SDS and CTAB and the standard partial molar volumes of transfer (Δ_trV_2,m⁰) of the amino acids and peptides to these aqueous surfactant solutions. The linear correlation of V₂⁰ for a homologous series of amino acids has been utilized to calculate the contribution of the charged end groups (NH₃⁺, COO⁻), CH₂ group and other alkyl chains of the amino acids to V₂⁰. The results on the partial molar volumes of transfer from water to aqueous SDS and CTAB have been interpreted in terms of ion–ion, ion–polar and hydrophobic–hydrophobic group interactions. The volume of transfer data suggests that ion–ion or ion–hydrophilic group interactions of the amino acids and peptides are stronger with SDS compared to those with CTAB. Comparison of the hydration numbers of amino acids calculated in the present studies with those in other solvents from literature shows that these numbers are almost the same at 1 mol · kg⁻¹ level of the cosolvent/cosolute. Increasing molality of the cosolvent/cosolute beyond 1 mol · kg⁻¹ lowers the hydration number of the amino acids due to increased interactions with the solvent and reduced electrostriction.     

Physicochemical investigation on interactions of some amino acids with aqueous tetra-butyl ammonium bromide solution at 298.15 K

Apparent molar volumes, viscosity B-coefficients, and apparent molar isentropic compressibilities of glycine, L-alanine, L-valine and L-leucine in 0.062, 0.125 and 0.256 mol kg^?1 aqueous tetra-butyl ammonium bromide (TBAB) solution have been determined at 298.15 K from their experimental density, flow time and sound speed measurements, respectively. The standard partial molar volumes and compressibilities are used to calculate the corresponding volume of transfer at infinite dilution, from water to aqueous TBAB solutions. The linear correlation of partial molar volumes for a homologous series of amino acids has been utilised to calculate the contribution of charged end groups and other alkyl chains of the amino acids to partial molar volumes. The hydration numbers of amino acids have also been determined. Viscosity B-coefficients have been calculated using the Jones–Dole equation. The values of the charged end groups contribution to the viscosity B-coefficients of the amino acids are calculated.     

Effects of solvation on partition and dimerization of benzoic acid in mixed solvent systems

The partition of benzoic acid between 0.1M perchloric acid solution and two kinds of mixed solvents has been carried out at 25 degrees C. The partition and dimerization constants of benzoic acid have been determined in the 1-octanol-benzene and 2-octanone-benzene systems. In both the mixed solvent systems, with increasing content of 1-octanol and 2-octanone in each mixed solvent, the partition constant of benzoic acid has been found to increase, and the dimerization constant of benzoic acid in each organic phase to decrease. These phenomena are attributable to solvation of monomeric benzoic acid by 1-octanol and 2-octanone molecules in each mixed solvent.     

The formation of heterodimers by vancomycin group antibiotics

The formation of heterodimers in mixtures of glycopeptide antibiotics has been detected by electrospray ionization mass spectrometry (ESI-MS), and dimerization constants have been determined. By using NMR spectroscopy, it has been shown that these heterodimers indeed exist in aqueous solution. The dimerization constants obtained by NMR spectroscopy are in good agreement with those determined by ESI-MS. Structural information on the heterodimer interface of some of the heterodimers is obtained by using two-dimensional NMR techniques and reveals that these heterodimers are similar in structure to the homodimers.