Physico-chemical behavior of bile salts

Roles and potential roles of bile salts in the human body and in health have been reviewed. The nomenclature of these biological amphiphiles, the mechanism of their formation in the liver and subsequent structural modifications in the enterohepatic cycle have been summarized. Emphasis has been placed on the controversies surrounding their physico-chemical properties, especially the patterns of their aggregation, and their ability to catalyze hydrolysis pathways in aqueous solution and to stimulate the activity of human milk lipase. The role of bile salts as biological surfactants and their participation in the dissolution of cholesterol gallstones, lipid solubilizatlon and absorption, and their ability to cause lysis of membrane surfaces has been discussed. Where possible, emphasis has been placed on the importance of the presence of monomers or small oligomers on the physico-chemical properties of these steroidal molecules.     

The thermal behavior of triethylenediammonium salts

(trienH₂)[CoCl₄], which contains tetrahedral chlorocobaltate(II) anions, decomposes under argon in two stages via a stepwise deprotonation of the cation. The decomposition starts at 310°C with the liberation of HCl, followed at 400°C by the simultaneous release of a further mole of HCl and triene and/or its cracking products. The second decomposition stage is strongly influenced by the atmosphere. In the lower temperature region (<400°C), increasing oxygen contents of the carrier gas lead to decreasing mass losses. Therefore, the solid residues contain various amounts of C,N-containing products as well as coke. The thermal decomposition of the iron(III) compound, which contains μ-oxalato-bridged FeCl₄ units, begins with the dehydratation followed by the decay of the complex anion to produce CO, CO₂, and HCl. Instead of a binuclear, monooxobridged chloroferrate(III) complex, a [FeCl₄]^? — containing compound is proposed as one of the final products. The third decomposition stage, partially overlaying the preceding one, is the degradation of the organic cation as found for the cobalt compound. The results of thein situ-TA-MS measurements are compared with those obtained from usual TA techniques as well as from the residue characterization by X-ray diffraction, Raman spectroscopy, and chemical analysis.     

Copolymerization of sodium acrylate with new acrylamide derivatives in the presence of water-soluble salts

Copolymerization of sodium acrylate with new acrylamide derivatives was studied. The copolymerization constants r1 and r2 of the monomers and the molecular weights of the copolymers were determined.     

Micellar behavior in solutions of bile-acid salts

Summary The density, electrical conductivity, viscosity, lightscattering and the low-angle X-ray diffraction have been examined in the solution region of the ternary systems of sodium cholate or desoxycholate and n-decanol and water at 20°. The phase diagrams show a continuous transition from homogeneous solutions of bile-acid salt in water to homogeneous solutions of bile-acid salt and water in decanol. Along the bile-acid salt-water axis there are micellar solutions containing micelles of the normal type where the polar groups are directed outwards, and these micelles can solubilize decanol without initially undergoing any change in their basic structure. Above a critical value, however, the micellar structure is determined by the decanol molecules, and at large decanol contents there is an inversion that results in the formation of reversed micelles, with the polar groups and water now located within the core of the micelles.

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Zusammenfassung Dichte, elektrische Leitfähigkeit, Viskosität, Lichtstreuung und Kleinwinkelstreuung von Röntgenstrahlen wurden im Lösungsgebiet der ternären Systeme Natriumcholat bzw. Natriumdesoxycholat, n-Dekanol und Wasser studiert. Das Phasendiagramm zeigt einen kontinuierlichen Übergang von der homogenen Gallensalzlösung in Wasser bis zur homogenen Lösung von Gallensalz und Wasser in Dekanol. Entlang der Gallensalz-Wasserachse kommen mizellare Lösungen vor, die Mizellen vom normalen Typ enthalten, bei denen die polaren Gruppen nach außen gerichtet sind. Diese Mizellen können recht große Mengen Dekanol solubilisieren, ohne daß ihre Grundstruktur verändert wird. Oberhalb einer kritischen Menge bestimmen jedoch die Dekanolmoleküle die Mizellstruktur. Bei großen Mengen Dekanol erfolgt eine Umstrukturierung, die zur Bildung von Mizellen mit den polaren Gruppen im Mizellkern führt.

     

Copolymerization of methacrylic acid alkali metal salts and polyether-containing monomers in solid polymer electrolytes

Copolymerization of methacrylic acid alkali metal salts (MAAM; M = Li, Na, K, Rb or Cs) and oligo(oxyethylene) methacrylate (MEO) was carried out in bulk or in poly(oligo(oxyethylene) methacrylate) (PMEO) at 60°C. The copolymers of MAAM and MEO which were obtained by bulk polymerization showed a cation conductivity of around 1 × 10^?7 S/cm at room temperature. On the other hand, the copolymers obtained by radical polymerization in PMEO, showed a higher cation conductivity (10^?6–10^?5 S/cm). Furthermore, higher cation conductivity was observed for the copolymer systems containing alkali metal cations with a larger ion radius. This tendency was explained by the strength of the bond between alkali metal cation and ether oxygens. The degree of dissociation had little effect on this difference in the conductivity. The effective dissociation of methacrylic salts was enhanced in the copolymer compared to the homopolymer because of the suppression of the adjacent dissociative carboxylic acid groups. Arrhenius plots for ionic conductivity show the migration of ions along with the segmental motion of the polymer matrix.     

Salting-out and ionic volume behavior of some tetraalkylammonium salts

Measurements of salting-out of Ar by NH ₄ Br and a series of homologous symmetrical tetraalkylammonium bromides in water are reported and discussed. A new gas-solubility apparatus is used enabling the solubility to be derived from a number of measurements on the same gas-solution sample at various pressures, rather than from a single measurement on each solution. Unexpectedly large salting-out effects are observed which increase with cation size. Electrostatic and nonelectrostatic effects are examined in relation to the ionic-volume behavior in water and methanol as a basis for discussion of the results. The relative electrostrictions of the TAA and Br^? ions in these two solvents are compared. Calculations based on electrostatic and scaled particle theory are compared, and it is concluded that the latter treatment obscures the electrochemical factors of essential interest in solute/solvent distribution about ions in solution.     

Phase behavior of DNA solutions in the presence of salts

The thermodynamic behavior of DNA solutions in the presence of salts is studied using a new phenomenological model of Helmholtz free energy of the system. The activity coefficient of the DNA–salt solution system is calculated and its asymptotic behavior suggests the formation of gel precipitate. Phase instability analysis of the derived free energy predicts multivalent salt concentration at which DNA precipitates. However the model is incapable to predict the redissolution of DNA at higher salt concentration.     

Thermochemical properties and thermokinetic behavior of energetic triazole ionic salts

The properties of dissolution in different solvents,the specific heat capacity and thermal decomposition process under the non-isothermal conditions for energetic triazole ionic salts 1,2,4-triazolium nitrate(1a),1,2,3-triazolium nitrate(1b),3,4,5triamino-1,2,4-triazolium nitrate(2a),3,4,5-triamino-1,2,4-triazolium dinitramide(2b)were precisely measured using a Calvet Microcalorimeter.The thermochemical equation,differential enthalpies of dissolution(△difH m ),standard molar enthalpies of dissolution(△difH ...     

Thermal behavior and dismantlability of adhesives containing various inorganic salts

As a fundamental study on the development of dismantlable adhesives containing chemically reactive materials, the thermal behavior and dismantlability of an epoxy adhesive containing one of the twenty-seven inorganic salts (chlorides, perchlorates, and nitrates) were observed. In the thermal behavior measured by the differential scanning calorimetry, epoxy adhesives with inorganic salts containing iron, copper, zinc, and aluminum cations released heats of reaction at lower temperatures than the adhesive alone or the adhesives with other inorganic salts. Since such inorganic salts were considered to be effective candidates as fillers in dismantlable adhesives, the adhesion strengths of their mixtures with the adhesive were observed after heat aging at 270 °C for 30 min. The results showed that both chloride and perchlorate salts specifically decreased the adhesion strength after heating. On the other hand, the effect of nitrate salts on the decrease in adhesion strength was low in comparison with the chloride and perchlorate salts.     

三唑含能离子盐的热化学性质和热动力学行为

用微量热技术测量1,2,4-三唑硝酸盐(1a)、1,2,3-三唑硝酸盐(1b)、3,4,5-三氨基-1,2,4-三唑硝酸盐(2a)、3,4,5-三氨基-1,2,4-三唑二硝酰胺盐(2b)4种三唑类含能离子盐的溶解过程热效应、比热容(283KT353K)及非等温条件下的热分解过程.用处理实验数据和理论计算方法获得了1a、1b、2a、2b溶解过程的热化学方程式、微分溶解焓、摩尔溶解焓、动力学方程式、活化能、指前因子、283～353K温区内比热容随温度变化的线性关系式、标准摩尔热容CpΘ,m和285～353K温区以298.15K为基准的焓、熵和Gibbs自由能函数值.计算了热分解反应的动力学参数、热力学参数以及评估了1a、1b、2a、2b对热的抵抗能力.得到了化合物性质与分子结构之间内在关系的信息.     

Copolymerization behavior of titanium imidazolin‐2‐iminato complexes

Monocyclopentadienyl titanium imidazolin‐2‐iminato complexes [Cp′Ti(L)X₂] 1a (Cp′ = cyclopentadienyl, L = 1,3‐di‐tert‐butylimidazolin‐2‐imide, X = Cl), 1b (X = CH₃); 2 (Cp′ = cyclopentadienyl, L = 1,3‐diisopropylimidazolin‐2‐imide, X = Cl); 3 (Cp′ = tert‐butylcyclopentadienyl, L = 1,3‐di‐tert‐butylimidazolin‐2‐imide, X = Cl), upon activation with methylaluminoxane (MAO) were active for the polymerization of ethylene and propylene and the copolymerization of ethylene and 1‐hexene. Catalysts derived from imidazolin‐2‐iminato tropidinyl titanium complex 4 = [(Trop)Ti(L)Cl₂] (Trop = tropidinyl, L = 1,3‐di‐tert‐butylimidazolin‐2‐imide) were much less active. Narrow polydispersities were observed for ethylene and propylene polymerization, but the copolymerization of ethylene/hexene led to bimodal molecular weight distributions. The productivity of catalysts derived from the dialkyl complex 1b activated with [Ph₃C][B(C₆F₅)₄] or B(C₆F₅)₃ were less active for ethylene/hexene copolymerization but yielded ethylene/hexene copolymers of narrower molecular weight distributions than those derived from 1a/MAO. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6064–6070, 2008     

Phase behavior and phase-transfer catalysis of tetrabutylammonium salts. Interface-mediated catalysis

The phase behavior and component composition of the coexisting phases in the tetrabutylammonium bromide (TBABr)/benzene/water/NaBr four-component system were strongly influenced by the temperature, TBABr content, and NaBr concentration. The phase-transfer catalytic activity of TBABr for the reaction of decyl methanesulfonate with sodium bromide was closely related to the phase behavior. Under O (oil-rich phase) + L (TBABr-rich liquid phase) + W (aqueous phase) triphase conditions, the influences of temperature and stirring speed on the phase-transfer catalytic activity were small compared with those under O + W biphase conditions. The addition of other quaternary salts that were able to form w/o aggregates in the O phase enhanced the TBABr catalytic activity even under O + W conditions. The relationship between phase behavior and catalytic activity of tetrabutylammonium chloride or iodide (TBACl or TBAI) was also examined. The results strongly suggested that the catalysis of TBAX was attributable to the interfacial reactions of TBAX with the substrate. The interface includes the water-oil microinterface formed in the microemulsion-like L phase as well as the bulk water-oil interface.     

Nonideal behavior of alkylammonium salts in organic solvents at elevated temperatures

Osmometric vapor-pressure-lowering measurements on toluene, butylbenzene, chlorobenzene, and chloronaphthalene solutions of several secondary, tertiary, and quaternary long-chain (at least five carbon atoms per chain) alkylammonium chlorides, bromides, thiocyanates, nitrates, and perrhenates in the temperature range between 50–130°C show an appreciable amount of molecular association. The extent (number of aggregated units) and/or the degree (size of aggregated units) of aggregation decreases with the number of carbon atoms per chain, the polarity of the solvent, and the temperature, but increases with the size of the anions and the solute concentration. The data were treated quantitatively in terms of activity coefficients via the Gibbs-Duhem relation and also in terms of specific oligomer formation. The latter treatment shows the salts to form a dimer and one (exceptionally two) higher oligomer, for which the association constants have been calculated.     

Polyelectrolyte behavior and conformation of poly-L-methionine S-methylsulfonium salts in aqueous solution

The influence of the species of counterion on the polyelectrolyte behavior and the conformation of poly-L -methionine S-methylsulfonium salts in aqueous solution was studied by viscometric, electrochemical, and optical measurements. The degree of binding of small counterions to charged polyions increases in the sequence: chloride ? bromide < iodide < thiocyanate. The conformations of chloride and bromide salts are independent of polymer concentration. On the contrary, iodide and thiocyanate salts indicate a conformational transition, probably from a random-coil conformation to an intermolecularly stabilized β-form, with the increase of polymer concentration. The results suggest the existence of a strong specific interaction between counterion and macroion in iodide and thiocyanate salt solutions at high polymer concentration.     

Photochemistry and initiation behavior of phenylethynyl onium salts as cationic photoinitiators

Phenyl(phenylethynyl)iodonium hexafluorophosphate and diphenyl(phenylethynyl)sulfonium hexafluorophosphate were synthesized for application as cationic photoinitiators using simple, straightforward methods. Quantification of the purity of the counterion was determined by FTIR analysis with subsequent mathematical peak deconvolution. Photodecomposition products for direct irradiation were determined in steady state photolysis experiments yielding diphenyl sulfide and phenyl(phenylethynyl) sulfide or iodobenzene, respectively, as main products. Heterolytic cleavage was proposed as main photodecomposition pathway because low yields of phenylacetylene radical recombination products and no photoproducts generated by phenyl radicals, including benzene, were detected. High activity as photoinitiators was verified by photo‐DSC experiments in direct irradiation and in photosensitized initiation using 9,10‐dibutylanthracene, 2‐isopropylthioxanthone, and surprisingly also benzophenone as sensitizers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3419–3430, 2009