Temperature effect on the partition and dimerization constant of benzoic acid

Making use of the regular solution theory with binary coefficients, the partition of benzole acid between aqueous benzene phases was investigated. ΔH, ΔS and ΔG thermodynamic functions associated with the hydration-corrected partition and dimerization were calculated. It was found that the partition was spontaneous at high temperatures and of the hydrates of benzoic acid, the monohydrate monomer was dominant at high temperatures.     

Effect of pressure on the dimerization of benzoic acid in n-heptane

Ultraviolet absorption spectra of benzoic acid in n-heptane were measured at 25°C and up to 640 MPa. The reaction volume for the cyclic dimerization of benzoic acid was estimated as 0.4 ±0.9 cm³ mol⁻¹ from the pressure dependence of the dimerization constant. This is much more positive than those for noncylic hydrogen-bond formations which are from −3 to −6 cm³ mol⁻¹. It is ascribed to a compensation between a reduction in the volume accompanying the hydrogen-bond formation and an increase accompanying the cyclization. These two contributions to the reaction volume are estimated quantitatively.     

Acid-catalyzed dimerization and aralkylation in divinylaromatic compound-aromatic solvent systems

On heating styrene and bis(4-vinylphenyl) ether or a linear unsaturated aromatic oligomer with terminal vinyl groups in aromatic solvents, depending on the temperature and concentration of toluene-p-sulfonic acid, there are obtained predominantly dimers and linear oligomers, and/or products of the alkylation of the aromatic solvent by the unsaturated monomers, dimers, and oligomers.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2566–2574, November, 1990.     

Anion-exchange in mixed solvent systems

A quantitative separation scheme for 15 radionuclides is presented. The scheme is based on group separation by means of anion-exchange resins using mixed solvent systems and subsequent separation of the groups into individual components by means of change of both eluting agent and resin type. The optimum working conditions for separation are established. Separation procedures are of good reproducibility and practically quantitative.     

Maleic acid solvation in mixed water-ethanol solvents

Heat effects of maleic acid dissolution in mixed water-ethanol solvents at 298.15 K are determined by means of calorimetry. A rise in exothermicity of maleic acid solvation is observed upon changes in the solvent copmosition in the direction of H₂O → EtOH, the minimum being at ∼0.2 mol fraction of EtOH.     

Anion exchange in mixed solvent systems

The diffusion of chlorocomplexes of some corrosion and fission products in anion exchange beads has been studied in mixed solvent media. The effects of variables on the kinetics of the exchange process by the batch and flow technique were examined. The strongly basic anion exchanger Dowex 2X8 in its Cl⁻ form was used in organic solvent—water—hydrochloric acid solutions. The dependence of the exchange rate on temperature, the viscosity of the solution, the mean resin particle diameter and the composition of the solution was studied. Film and particle diffusion coefficients were calculated from the experimental data. The results provide valuable data for the design of separation procedures.     

非水混合溶剂体系的盐效应

采用改进的Rose釜测定了在101.33kPa下, 甲醇-二氧六环-NaSCN, 甲醇-二氧六环-NaI和甲醇-四氢呋喃-LiCl, 甲醇-四氢呋喃-CuCl2体系的汽液平衡数据。实验结果和热力学基本原理确证了体系的沸点与加入盐浓度间的线性关系, 计算了各双液组成下体系的盐效应常数, 分析了实验中产生"异常"现象的原因, 探讨了溶液内部粒子相互作用的规律, 通过用相律、盐效应理论、静电理论、溶剂化理论的解释, 得到了一些具有理论价值的结论。     

Solubility of pyrene in simple and mixed solvent systems

The solubility of pyrene was experimentally determined in simple and complex solvent systems (single, binary, ternary, quaternary and pentinary solvent systems) composed of benzene, ethylbenzene, hexane, hexanol and methylcyclohexane over a temperature range from 293 to 318 K. In addition, six models were used in this study to represent pyrene solubility in the different solvent systems. The interaction parameters for modified Wilson, NIBS/Redlich-Kister, UNIQUAC and NRTL models were estimated using the solubility data generated for pyrene in single, binary and ternary solvent systems. By re-adjusting the interaction parameters reported for Dortmund UNIFAC and ASOG models, a better representation of the solubility of pyrene was obtained compared to using reported values. Furthermore, a correction term is introduced for the ASOG model in this study to better improve pyrene solubility prediction in simple and mixed solvent systems. These estimated or re-adjusted interaction parameters for the different models, along with the reported parameters for Dortmund UNIFAC and ASOG models, were tested on complex solvent systems (quaternary and pentinary solvent mixtures), in order to check their validity and accuracy for such predictions.     

尿素-水混合溶剂中硫酸热力学性质的研究

本文应用电动势法测定下面无液接电池在278．15-318．15K温度范围内的电动势。     

Thermodynamics of dissolving and solvation processes for benzoic acid and the toluic acids in aqueous solution

Experimental data are presented for the solubility in water of benzoic and toluic acids from 5° to 65°C. From the solubility the molality of the monomeric form of the acid is calculated using literature data for both ionization and dimerization of the acid. These data for the monomer combined with data from the literature for vaporization of the solid and ionization in both the gas phase and the aqueous phase yield entropy and enthalpy changes for the solvation of molecular and anionic forms of the acid. A similar procedure is also applied to literature data for the solubility of benzene in water. It is shown that the hydration entropies of the monomeric forms are a linear function of their partial molar volumes. It is concluded that hydration of the undissociated o-toluic acid may be crucial to the increased acidity of that acid compared to benzoic acid.     

Change in heat capacity upon the solvation of alkali metal ions in N-methylpyrrolidone and mixed N-methylpyrrolidone-water solvent

The change in heat capacity upon ion solvation ??_solv C _p,i ^o in N-methylpyrrolidone (MP) and in mixed MP-water solvent is presented as the sum of three contributions: electrostatic, cavity formation, and changes in the structure of the solvent. The values for the electrostatic and cavity formation contributions are calculated using model concepts. The values of the structural contribution are determined. The obtained data was analyzed in dependence on the solvent??s composition and the electrostatic ion parameters.     

Anion-exchange studies of metal thiocyanates in aqueous and mixed solvent systems

The anion-exchange behaviour of metal ions in aqueous NH(4)CNS and aqueous NH(4)CNS-organic solvent mixtures has been studied. The effect of the pH and the concentrations of thiocyanate and organic solvent on the distribution coefficients has been investigated. Fifteen binary metal ion separations are reported.     

Investigations of salt — Mixed solvent systems XXXVIII. Crystallization enthalpy of magnesium chloride in mixed solvent systems

The crystallization enthalpies of MgCl₂ in MgCl₂–H₂O-cosolvent systems at 25°C were determined calorimetrically as a function of the cosolvent content in the mixed solvent. Methanol, acetone, and N,N-dimethylformamide were employed as cosolvents. The results show the individual cosolvents to have very differently influences on the energy state of the salt in the saturated solution. The most pronounced changes are effected by an increase of the DMF content in the mixed solvent. The intensity of Mg²⁺-DMF interaction at a higher DMF content in the saturated solution considerably exceeds the Li⁺-DMF interaction in LiCl solutions.     

Distribution ratio, distribution constant and partition coefficient. Countercurrent chromatography retention of benzoic acid

There is some confusion in chromatography between terms such as solute distribution ratio, distribution constant and partition coefficient. These terms are very precisely defined in the field of liquid-liquid systems and liquid-liquid extraction as well as in the field of chromatography with sometimes conflicting definitions. Countercurrent chromatography (CCC) is a chromatographic technique in which the stationary phase is a support-free liquid. Since the mobile phase is also liquid, biphasic liquid systems are used. This work focuses on the exact meaning of the terms since there are consequences on experimental results. The retention volumes of solutes in CCC are linearly related to their distribution ratios. The partition coefficient that should be termed (IUPAC recommendation) distribution constant is linked to a single definite species. Using benzoic acid that can dimerize in heptane and ionize in aqueous phase and an 18 mL hydrodynamic CCC column, the role and relationships between parameters and the consequences on experimental peak position and shape are discussed. If the heptane/water distribution constant (marginally accepted to be called partition coefficient) of benzoic acid is 0.2 at 20 °C and can be tabulated in books, its CCC measured distribution ratio or distribution coefficient can change between zero (basic aqueous mobile phase) and more than 25 (acidic aqueous mobile phase and elevated concentration). Benzoic acid distribution ratio and partition coefficient coincide only when both dimerization and ionization are quenched, i.e. at very low concentration and pH 2. It is possible to quench dimerization adding butanol in the heptane/water system. However, butanol additions also affect the partition coefficient of benzoic acid greatly by increasing it.