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Methods are examined for estimating the Hildebrand solubility parameter of a mixture of organic solvents using the characteristics of their structural elements. A procedure is proposed for calculating the solubility parameter for mixtures of solvents differing in composition and structure depending on the ratio of their components. These results enable us to predict the optimal solvent mixture composition for polymers with a known Hildebrand solubility parameter. The proposed method permits us to estimate the solubility of complex mixtures of hydrocarbons of petroleum origin such as the tar obtained as the vacuum residue of oil distillation when it is used as a polymer solvent. 1H NMR analysis results were used to determine the structural elements of a tar and calculate its Hildebrand solubility parameter. [ABSTRACT FROM AUTHOR]

L-pipecolic acid (L-PA) is a key chiral intermediate in the synthesis of many important drugs. However, there is a lack of research on the efficient extraction and purification process for L-PA. Here, eleven different organic solvents were evaluated for selective extraction of L-PA by physical extraction. Among these solvents, methyl ethyl ketone (MEK) showed the highest extraction yield of L-PA, and analysis of the linear solvation energy relationship between the solvents showed that MEK was the most suitable solvent for L-PA extraction. The highest extraction yield of L-PA was 37% under optimal conditions (pH 6, 20°C, 30 min and ratio of 1). Furthermore, the repetitive extraction of L-PA from bioconversion solution was also investigated. The MEK gave high purity of L-PA (93.1% and 22.8% yield) from the bioconversion mixture. Our study is the first approach to show easy recovery of L-PA by liquid-liquid extraction and the application of MEK extraction method to L-lysine bioconversion mixture. [ABSTRACT FROM AUTHOR]

1,3,5-Tris(2-diphenylphosphoryl-4-ethylphenoxymethyl)benzene (L′), a phosphorylcontaining tripodand, was synthesized for the first time in order to find extraction systems for efficient recovery of lanthanides. The main regularities of extraction of lanthanide(III) ions with mixtures of L′ and 4-benzoyl-5-methyl-2-phenyl-3-pyrazolone (HL) into CHCl3, 1,2-dichloroethane, toluene, and carbon tetrachloride from chloride solutions were elucidated. A significant synergistic effect, associated with the formation of hydrophobic mixed-ligand complexes of lanthanides(III), was found. The stoichiometry of the extracted complexes was determined by the equilibrium shift method. The equilibrium constants and values of the synergistic effect in the LnIII—L′—HL—dichloroethane system were calculated. The influence of the nature of the organic solvent and the composition of the aqueous phase on the efficiency of lanthanide(III) ion extraction into the organic phase was considered. [ABSTRACT FROM AUTHOR]

Extraction of rare earths(III) from hydrochloric acid solutions with mixtures of new tridentate carbamoylmethylphosphine oxides Ph2P(O)CH2CON(R)CH2CH2P(O)Ph2 (R = Me, Bu, Oct) and 4-benzoyl-3-methyl-1-phenyl-1H-pyrazol-5(4H)-one in organic solvents has been studied. The observed strong synergistic effect has been attributed to the formation of hydrophobic mixed-ligand rare earth complexes in the organic phase. Stoichiometry of the extractable complexes has been determined, and extraction constants have been calculated. The effect of organic solvent and composition of the aqueous phase on the extraction efficiency has been analyzed. [ABSTRACT FROM AUTHOR]

Extraction of rare-earth elements(III) ions from chloride solutions with mixtures of 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone and phosphoryl-containing podands in organic solvents has been studied. The observed significant synergistic effect is associated with the formation of hydrophobic mixed-ligand complexes of rare-earth elements(III). The stoichiometry of the extracted complexes has been determined, and the extraction constants have been calculated. The influence of the phosphoryl-containing podand structure, the organic solvent nature, and the aqueous phase composition on the efficiency of the extraction of rare-earth element(III) ions into the organic phase has been considered. [ABSTRACT FROM AUTHOR]

The possibility of preparing a biomaterial based on a mixture of biocompatible and biodegradable polymers, polyhydroxybutyrate and polycaprolactone, was studied. Samples for laboratory tests were prepared by forming films from an emulsion of solutions of biologically active compounds in a solution of the polymers in an organic solvent. Trypsin was used as the proteolytic component. Films containing chlorhexidine digluconate, pefloxacin, and furazolidone were studied in order to find the optimum antimicrobial component. The optimum composition of the molding mixture for preparing films with the optimal properties, i.e., trypsin activity 52.5% of the initial value, vapor permeability 4.5 mg/cm2, furazolidone desorption rate 25% C/ C, and properties 90% stable after storing in normal saline, was determined. [ABSTRACT FROM AUTHOR]

Thermodynamic characteristics of mixtures of aprotic amides with water and organic solvents with hydrogen bond networks are calculated. Within a model approach the specific and non-specific components of the total energy of the intermolecular interaction are determined, based on which the corresponding contributions to the enthalpies of component mixing are calculated. It is found that negative enthalpies of mixing in the mixtures under study are due to non-specific interactions rather than heterocomponent specific ones. It is shown that the difference in the structural-thermodynamic characteristics of aqueous and nonaqueous mixtures of aprotic amides is mainly caused by packing features of solutions and the behavior of hydrogen bond networks of water and organic solvents. [ABSTRACT FROM AUTHOR]

The wetting time of porous electrodes with electrolytes based on organic solvents and ionic liquids, respectively, was investigated with two different techniques: with a tensiometer and by impedance spectroscopy. The results of this study showed that the wetting time of a porous electrode with ionic liquid-based electrolytes is up to 20 times longer than that with electrolytes comprising organic solvents. A significant reduction in the wetting time with ionic liquid-based electrolytes could be achieved by adding organic solvents. This effect can be explained by the interplay of reduced viscosity, increased surface tension and change in contact angle caused by the addition of the organic solvent, with the lower viscosity being the main driver of improved wetting kinetics. [ABSTRACT FROM AUTHOR]

A mathematical model is presented for the kinetic resolution of racemates. It takes all intermediate binding steps into account and assumes that such steps are reversible. The model describing dynamics of the chiral reaction products consists of two nonlinear differential equations. With this model, the enantioselectivity of enzyme has been studied. Mathematical and numerical simulation of the model show that there are several ways to control the enantiomeric ratio (E) but the affinity and the binding rates of the intermediate enzyme complex to the racemic substrates are the key steps for the enzyme enantioselectivity. [ABSTRACT FROM AUTHOR]

The effects of polymer charge density on the counterion-specific and solvent-specific coil-globule transition of polycarboxylates were investigated for alkali metal salts of poly(styrene-alt-maleic acid) (PSaltMA) and poly(acrylic acid) (PAA) in aqueous organic solvent mixtures. The order of the transition region, namely, the counterion specificity for the transition in, e.g., aqueous dimethyl sulfoxide (DMSO), was the same for both polyelectrolytes, Na > K > Cs > Li, while the discrepancy of the transition region between Na and Li systems was appreciably narrower for PSaltMA (approximately 20 vol%) than that of PAA (approximately 29 vol%). Such diminished counterion specificity for the former was ascribed to the nonuniform charge array. Namely, PSaltMA has two kinds of nearest charge arrays, one is the shorter spacing between the maleic acid carboxyl groups and the other is the longer one via one styrene group. Thus, the former may be favorable for binding of the smaller counterion (i.e., Li) and the latter for the larger one (Cs). Such a 'size-fitting effect' for the counterion binding was in fact further confirmed with variously neutralized PAAs. For example, the counterion specificity in aqueous DMSO of PAA40 that was neutralized to 40 % was Cs > K > Na > Li, showing that the largest counterion becomes most favorable in inducing the transition with increasing average charge spacing. In fact, the nuclear magnetic resonance line width measurement for Cs suggested that the counterion binding strength of the large counterion for PAA increases with decreasing charge density from 100 to 40 % neutralization. [ABSTRACT FROM AUTHOR]

Poly(vinylidene fluoride) (PVDF) membranes possessing interconnected bicontinuous structures with superior mechanical properties and improved hydrophilicity were obtained from PVDF/ N, N-dimethylacetamide (DMAc)/Tween 80/water systems via non-solvent induced phase separation (NIPS) with 60 °C and ambient temperature casting solution. Tween 80/HO mixtures were adopted as dopant; water/ethanol (50:50, mass ratio) and ethanol were chosen as coagulants. The effects of process parameters in terms of variations in dopant contents, casting solution temperatures, and coagulant compositions on the phase inversion process and performance of the resultant membranes were investigated. During the demixing process, water diffused from the interior of Tween 80 reverse micelles, resulting in an accelerated precipitation rate and surface segregation process of the polar head groups of Tween 80. The high temperature of the casting solution contributed to enhancing the diffusion rate of liquid-liquid demixing on crystallization. The coagulant compositions changed the liquid-liquid and solid-liquid demixing dynamics of the casting solutions. Ethanol coagulant contributed to crystallization of PVDF/DMAc/Tween 80/water systems prior to liquid-liquid demixing. This delayed demixing process favored the formation of porous foliage-type top structures with fibril or lath bicontinuous fine structure of membrane bulk, increasing flux, and significant hydrophilicity improvement. Casting solutions in water/ethanol coagulant exhibited a less delayed demixing process with both liquid-liquid demixing and crystallization, resulting in formation of fine structure in the form of strings or stripes and limited hydrophilicity improvement. The predominant typical α- and β-type crystallinity in PVDF was attributed to the existence of dopants, the high temperature of the casting solution, and water/ethanol coagulant. This was consistent with the superior mechanical properties of the corresponding PVDF membrane. The newly developed hydrophilic PVDF membranes with superior mechanical properties and low-fouling of bovine serum albumin (BSA) are anticipated to be suitable not only for wastewater treatment, but also for bioseparation. [ABSTRACT FROM AUTHOR]

The results of calorimetric investigations of electrolyte solutions in the mixtures of water, methanol, N, N-dimethylformamide, and acetonitrile with numerous organic cosolvents are discussed with regard to the intermolecular interactions that occur in the solution. Particular attention is given to answer the questions how and to what extent the properties of the systems examined are modified by the cosolvent added and how much the properties of the cosolvent are revealed in the mixtures with the solvents mentioned above. To this goal, the analysis of the electrolyte dissolution enthalpies, single ionic transfer enthalpies, and enthalpic pair interaction coefficients as well as the preferential solvation (PS) model are applied. The analysis performed shows that in the case of the dissolution enthalpies of simple inorganic electrolytes in water-organic solvent mixtures, the shape of the dependence of the standard dissolution enthalpy on the mixed solvent composition reflects to a large extent the hydrophobic properties of the organic cosolvent. In the mixtures of methanol with organic cosolvents, the ions are preferentially solvated either by methanol molecules or by molecules of the cosolvent, depending on the properties of the mixed solvent components. The behavior of inorganic salts in the mixtures containing N, N-dimethylformamide is mostly influenced by the DMF which is a relatively strongly ion solvating solvent, whereas in acetonitrile mixtures, the thermochemical behavior of electrolyte solutions is influenced to a large extent by the properties of the cosolvent particularly due to the PS of cation by the cosolvent molecules. [ABSTRACT FROM AUTHOR]

4-Hydroxy-3-methyl-4′-benzeneazo(azobenzene) is used as an inhibitor to study the kinetics of radical generation upon cumyl hydroperoxide or tert-butyl hydroperoxide decomposition in microemulsions formed in the presence of cationic surfactants in organic solvents and on the surface of montmorillonite particles modified with cationic surfactants. It is demonstrated that, in contrast to microemulsions, at comparable surfactant contents, modified montmorillonite has almost no effect on the decomposition rate of hydro-peroxides. A considerable catalytic effect is only detected after Cu(2+) ions (≤0.1 wt %) are additionally applied onto the surface of its nanoparticles. The addition of polar solvents dramatically decelerates the decomposition of hydroperoxides. The activation energies of the reaction are determined for the dispersions of modified montmorillonite in toluene (56 kJ/mol) and toluene-ethanol mixture (69 kJ/mol). [ABSTRACT FROM AUTHOR]

Two data analysis programs of Sedfit and VelXLAI associated with analytical ultracentrifugation were compared with each other for the sedimentation analysis of a pure polystyrene polymer solution as well as solutions of polymer mixtures in organic solvent containing two components in different mixing ratios. Interference detection optics was used for the sedimentation analysis. The pure polymer showed concentration dependency of the sedimentation coefficient and the results were similar in both the programs. In the mixture samples, slight differences in the peak sedimentation coefficients of the two polymers fractions in the analysis programs were observed. However, VelXLAI program was observed to detect the relative fractions of the two mixture components more accurately than Sedfit. [ABSTRACT FROM AUTHOR]

Precipitation from alcohol used against fractionation of polysaccharides was applied as an energy-efficient chemical modification with only a co-precipitation of polysaccharide and the modifying agent in polar organic solvents, and drying. Addition of ethanol caused a conformational change of polysaccharides with increasing intramolecular hydrogen bonding and a dense structure in close proximity to atoms, especially, in the presence of modifying agents. Extent of modification depended on the structure of polysaccharides and pH in polar organic solvents. The co-precipitates in polar organic solvents seem to act as a precursor while still maintaining the integrity of the modified polysaccharides. Eventually, a small amount of polar organic solvents (1.5 times volume to the weight of the mixtures) to disperse the reaction mixtures was enough to complete modification. [ABSTRACT FROM AUTHOR]

Abstract  Poly(terephthalamide) microcapsules can be reproducibly and easily prepared by interfacial polycondensation around emulsion droplets in water. Oil drops of cyclohexane/chloroform mixture stabilized with poly(vinyl alcohol) containing terephthaloylchloride serve as soft template. The interfacial polycondensation starts immediately after addition of an amine mixture (hexamethylenediamine/diethylenetriamine). Light and scanning electron microscopy prove the formation of capsules with size distribution in the range from a few up to 100 µm depending on particular composition of the reaction mixture. The morphology of the capsule wall is characterized by precipitated particles. If instead of pure organic solvents a reactive oil phase is used as template, the capsules can serve in subsequent reactions as templates for the synthesis of composite particles. In this way, styrene can be radically polymerized inside the capsule leading to composite capsules. The capsule morphology is determined by the partition of all components between all phases. [ABSTRACT FROM AUTHOR]

Abstract  The enthalpies of solution of benzo-15-crown-5 ether in methanol–water mixtures and methanol–water–sodium iodide systems have been measured at 298.15 K. The values of standard enthalpies of solution of benzo-15-crown-5 ether are positive in the mixtures of water and methanol within the whole range of mixture composition. The equilibrium constants of complex formation of benzo-15-crown-5 ether with the sodium cation have been determined by conductivity measurements at 298.15 K. The thermodynamic functions of the formation of these complexes have been calculated. The Gibbs energy of complex formation depends on the base–acid properties of methanol–water mixture. [ABSTRACT FROM AUTHOR]

A procedure was developed for conversion of spent UNEX solvent into a solid infusible resin, insoluble in aqueous alkali and acid solutions and organic solvents, by condensation with phenol and paraform. Incorporation of phenyl trifluoromethyl sulfone into the resin was confirmed by physicochemical methods. Resistance of the cured resin to high temperatures was proved by thermogravimetry. The developed procedure can also be applied to other organic wastes containing weakly reactive aromatic compounds such as nitrobenzotrifluoride, 1,2-dichlorobenzene, and nitrobenzene. [ABSTRACT FROM AUTHOR]

This paper describes a potentiometric titration method for the determination of stoichiometric autoprotolysis constants (pKs) in binary mixtures of water with methanol, ethanol, 1-propanol, 2-propanol, dioxane, and acetonitrile. A combined pH electrode modified by replacing its aqueous KCl solution with 0.01 M NaCl + 0.09 M NaClO4 saturated with AgCl was used for the first time in aqueous organic solvent mixtures. The potentiometric cell was calibrated before each experiment so that the hydrogen ion concentration rather than the activity was measured. The calibration constants E° and k were determined by titrating a solution of perchloric acid with sodium hydroxide solution for each medium studied at 25 °C and under nitrogen atmosphere. During each titration the concentration of NaClO4 was maintained at 0.1 M and the pKs values were calculated by using this titration data. It is shown that the combined electrode system could be successfully used to determine autoprotolysis constants in water-organic solvent mixtures. Furthermore, the variation of the pKs values with solvent composition is discussed. [ABSTRACT FROM AUTHOR]

Cyclohexanol nitration by a mixture of ammonium nitrate and sulfuric acid in the presence of an organic solvent was studied. [ABSTRACT FROM AUTHOR]