Increasing fluorous partition coefficients by solvent tuning

Low partition coefficients of fluorous components have been a persistent problem in liquid-liquid separations using perfluoroalkanes as the fluorous phase. Solvent tuning of both the nonfluorous and the fluorous phase dramatically enhances the partitioning of light or polar fluorous molecules into the fluorous liquid phase, while minimally effecting partition coefficients of nonfluorous molecules. These findings suggest an expanded scope for liquid-based separations in fluorous biphasic catalysis, fluorous-tagged reagents, fluorous-supported oligomer synthesis, and related areas. [reaction: see text]     

Perfluoroalkylated-pyridine catalyzed Aldol condensations of aldehydes and ketones in a fluorous biphasic system without fluorous solvent

Aldol condensation of different ketones with various aromatic aldehydes proceeds efficiently in the presence of catalytic amount of perfluoroalkylated-pyridine in a fluorous biphasic system without fluorous solvent, which has prompted various concerns involving cost, solvent leaching, and environmental persistence. The catalyst can be recovered by simple cooling and precipitation and used again.     

New axially dissymmetric ligand recoverable with fluorous solvent

Axially dissymmetric ligands with perfluoroalkyl groups, (Ra)-2,2′-bis[(R)-1-hydroxy-1H-perfluorooctyl]biphenyl [(Ra)-(R)₂-1c] and its enantiomer, have been synthesized successfully by the coupling reaction of the corresponding aryl bromide using Ni(COD)₂. These ligands showed much higher asymmetric induction in the reaction of various aldehydes with diethylzinc than the trifluoromethyl (1a) or pentafluoroethyl (1b) analogues. Furthermore, 1c was recovered quantitatively by extraction with a fluorous solvent from the reaction mixture due to its high fluorine content. The recovered ligand 1c was pure enough to be reused without purification. The efficiency of 1c as the chiral ligand was not decreased at all even after seven times recycling.     

有机溶剂/缓冲液两相体系中全细胞催化拆分环氧氯丙烷

研究了有机溶剂/缓冲液两相体系中重组大肠杆菌E.coli BL21 (DE3)全细胞水解动力学拆分外消旋环氧氯丙烷制备(R)-环氧氯丙烷的过程.结果表明,最适反应条件为:最适有机溶剂异辛烷与缓冲液的体积比7:3,最适缓冲液pH 8.0,底物浓度574mmol/L,全细胞加入量0.07g湿菌体/ml溶液,温度30℃.在此条件下于1L反应器中反应45min,(R)-环氧氯丙烷的摩尔产率、光学纯度和时空产率分别达到37.5%,99.3%ee和0.286mol/(L·h).与单一水相体系相比,异辛烷/缓冲液两相体系中底物浓度和(R)-环氧氯丙烷时空产率分别提高了55.2%和98.6%.     

A novel ytterbium/perfluoroalkylated-pyridine catalyst for Baylis-Hillman reaction in a fluorous biphasic system

Ytterbium perfluorooctanesulfonate [Yb(OPf)₃] catalyses the highly efficient Baylis-Hillman reaction in the presence of a catalytic amount of a novel perfluoroalkylated-pyridine as a ligand in a fluorous biphasic system (FBS) composed of toluene and perfluorodecalin. The new process can be carried out successfully without the use of a stoichiometric amount of Lewis base. The fluorous phase containing the active catalytic species is easily separated and can be reused several times without significant loss of catalytic activity.     

New bis(fluoro-ponytailed) bipyridine ligands for Pd-catalyzed Heck reactions under fluorous biphasic catalysis condition

Three highly fluorinated bipyridine derivatives (4,4′-bis(R_fCH₂OCH₂)-2,2′-bpy) {R_f=HCF₂(CF₂)₇ (1a), n-C₈F₁₇ (1b), n-C₁₀F₂₁ (1c)} have been synthesized using 4,4′-bis(BrCH₂)-2,2′-bpy and the corresponding fluorinated alkoxides. The fluorine contents of ligands 1a-c are 58.3, 59.8, and 62.3%, respectively. Despite its high fluorine content, the ligand 1a with a -CF₂H polar terminal group is more soluble in organic solvents. The ligand 1b is a white solid and is still moderately soluble in CH₂Cl₂. The ligand 1c has a high fluorophilicity, the partition ratio being 42:1 for the n-C₈F₁₈/CH₂Cl₂ system. The reaction of ligands 1a-c with [PdCl₂(CH₃CN)₂] results in the novel Pd complexes [PdCl₂(4,4′-bis-(R_fCH₂OCH₂)-2,2′-bpy)] where R_f=HCF₂(CF₂)₇ (2a), n-C₈F₁₇ (2b), n-C₁₀F₂₁ (2c), respectively. The Pd complex 2b is a pale yellow solid, and has been tested unsatisfactorily for FBC. Insoluble in organic solvents, the Pd complex 2c dissolves only in fluorinated solvents, for instance FC77, which is mainly n-C₈F₁₈. The novel Pd complex 2c has been tested as a catalyst in Heck reactions under a fluorous biphasic catalysis condition. It was found that the Pd complex 2c, after an easy separation, keeps its catalytic activity (>90% yield), even after seven runs. The TGA studies indicate that the Pd complexes 2a-c are stable up to 330 °C.     

Extended electrochemical windows made accessible by room temperature ionic liquid/organic solvent electrolyte systems.

The electrochemical windows of acetonitrile solutions doped with 0.1 M concentrations of several ionic liquids were examined by cyclic voltammetry at gold and platinum microelectrodes. These results were compared with those observed in the commonly used 0.1 M tetrabutylammonium perchlorate/acetonitrile system as well as with neat ionic liquids. The use of a trifluorotris(pentafluoroethyl)phosphate-based ionic liquid, specifically, as supporting electrolyte in acetonitrile solutions affords a wider anodic window, which is attributed to the high stability of the anionic component of these intrinsically conductive and thermally robust compounds.     

碳纳米复合物作为催化剂和乳化剂用于水/有机两相体系反应(英文)

This mini-review summarizes some novel aspects of reactions conducted in aqueous/organic emulsions stabilized by carbon nanohybrids functionalized with catalytic species. Carbon nanohybrids represent a family of solid catalysts that not only can stabilize water-oil emulsions in the same fashion as Pickering emulsions, but also catalyze reactions at the liquid/liquid interface. Several exam-ples are discussed in this mini-review. They include (a) aldol condensation-hydrodeoxygenation tandem reactions catalyzed by basic (MgO) and metal (Pd) catalysts, respectively; (b) Fischer-Tropsch synthesis catalyzed by carbon-nanotube-supported Ru; and (c) emulsion polymerization of styrene for the production of conductive polymer composites. Conducting these reactions in emul-sion generates important advantages, such as increased liquid/liquid interfacial area that consequently means faster mass transfer rates of molecules between the two phases, effective separation of products from the reaction mixture by differences in the water-oil solubility, and significant changes in product selectivity that can be adjusted by modifying the emulsion characteristics.     

Acid-base equilibria in binary water/organic solvent systems Dissociation of citric acid in water/dioxan and water/methanol solvent systems at 25 degrees

The thermodynamic constants of citric acid were determined at 25 degrees in water/dioxan and water/methanol mixtures with 10, 20, 30, 40 and 50% v/v organic co-solvent content. Simple relations allowing the calculation of palpha*(H) of citrate buffer solutions are proposed (alpha*(H) being the hydrogen-ion activity referred to the standard state in the corresponding medium). The palpha*(H) values of some citrate buffer solutions, suitable for standardization, are reported. The pK values obtained are discussed in relation to the nature and composition of the solvent, as well as the structure of the acid molecule.     

Acid-base equilibria of some pyridinol derivatives in binary water/organic solvent systems

Summary pK _a values of 2-hydroxy 3-pyridinol (HHP), 2-mercapto 3-pyridinol (MHP), and 2-carboxy-3-pyridinol (CHP) were determined by potentiometric titration in water/organic solvent mixtures containing 20 mole% of organic solvent at 25±0.1 °C and 0.1M ionic strength (KNO₃) applying an empiricalpH correction for mixed aqueous solvents. The influence of the organic solvents on the dissociation constants and tautomeric equilibria of the pyridinol derivatives is discussed. The effect of the molecular structure of the compounds onpK _a is also explained. Titrations of a mixture of two weak diprotic acids (HHP andCHP) in a water/dimethylsulphoxide medium containing 20 mole% organic solvent at constant ionic strength were evaluated using theGran method.

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Säure-Basen-Gleichgewichte einiger Pyridinolderivate in binären Systemen aus Wasser und organischen Lösungsmitteln

Zusammenfassung DiepK _a-Werte von 2-Hydroxy-3-pyridinol (HHP), 2-Mercapto-3-pyriodinol (MHP) und 2-Carboxy-3-pyridinol (CHP) wurden durch potentiometrische Titration in wäßrigen Systemen mit 20 mol% organischem Lösungsmittelanteil bei 25±0.1 °C und einer lonenstärke von 0.1M KNO₃ unter Anwendung einer empirischenpH-Korrektur für Lösungsmittelgemische bestimmt. Der Einfluß der organischen Lösungsmittel auf die Dissoziationskonstanten und die tautomeren Gleichgewichte der untersuchten Verbindungen und der Einfluß der molekularen Strukturen auf diepK _a-Werte werden diskutiert. Die Titration eines Gemisches von zwei schwachen zweibasigen Säuren (HHP undCHP) in Wasser/Dimethylsulfoxid bei konstanter Ionenstärke wurde mit Hilfe derGranschen Methode ausgewertet.

     

Thermodynamics of partitioning of benzocaine in some organic solvent/buffer and liposome systems

The thermodynamics of partitioning of benzocaine (BZC) were studied in octanol/buffer (ROH/W), isopropyl myristate/buffer (IPM/W), cyclohexane/buffer (CH/W), and dimyristoyl phosphatidylcholine (DMPC) and dipalmitoyl phosphatidylcholine (DPPC) liposome systems. In all cases the partition coefficients were greater than unity; therefore the free energies of transfer were negative, that is, the processes of transfer of BZC from aqueous media to organic systems were spontaneous. The partition coefficients were approximately three-fold higher in DMPC liposomes compared with the ROH/W system in the 30 degrees -40 degrees C temperature range. The enthalpies of transfer from aqueous media to ROH and IPM were negative, but positive for CH, while this property was negative for DMPC liposomes and positive for DPPC liposomes. The entropies of transfer were positive in almost all cases, except for DMPC. The results presented here confirm the lipophilic nature of BZC.     

用有机溶剂提纯六氟磷酸锂粗品

本文用乙醚作为纯化溶剂,采用有机溶剂重结晶并辅以洗涤萃取等方法来提纯六氟磷酸锂(LiPF6)粗品。工艺操作条件温和、能耗低、原材料无毒无HF腐蚀、简便易得,是一条绿色工艺纯化路线。经红外光谱、X射线粉末衍射对提纯后的晶体LiPF6进行结构确认和物相分析,对最终产品LiPF6中氯离子(Cl-)、乙二醇二甲醚(DME)不溶物和乙醚残留量进行检测分析,还探讨了残留的乙醚对锂离子二次电池首次充放电性能的影响。结果表明:LiPF6粗品经乙醚提纯后纯度达到99.98%,优于商用LiPF6;产品中微量乙醚残留不会对锂离子二次电池首次充放电性能造成不良影响。     

Development apparatus for thin-layer gel chromatography in organic solvent systems

An apparatus is devised for development of thin-layer gel chromatograms, which is easy to handle and gives reproducible results even with volatile organic solvent systems. The print technique with a silicone-treated paper can facilitate detection of the samples chromatographed.     

Colloidal suspensions of N-modified graphene nano-platelets in water and organic solvent/water mixed systems

The production of colloidal suspensions of graphene-based nano-platelets in large scale is highly important for their use in practical applications. In this work, we developed a new route for generation of colloidal suspensions of N-modified graphene-based nano-platelets (A-rG-O) with high concentration in water or organic solvent/water mixed systems by the reaction between graphene oxide and ammonium hydroxide. Graphene oxide was reduced by the ammonium hydroxide and N atoms (up to 6 at%) were introduced into A-rG-O materials using solution process without further thermal treatment. Such A-rG-O nano-platelets were well dispersed as individual layers in both systems. Macroscopic free-standing A-rG-O paper materials with good electrical conductivity were produced by filtration of such colloidal suspensions.     

Optimization of enzyme catalyzed peptide synthesis in a “water - water-immiscible organic solvent” biphasic system

Optimal conditions were found, for enzymatic synthesis of the dipeptide, N-acetyl-L-tryptophanyl-L-leucine amide in the biphasic system water - ethyl acetate. The synthesis was carried out using both free and. immobilized α-chymotrypsin. Optimization was performed, by such parameters as the “organic phase/aqueous phase” volume ratio, the pH of aqueous phase, and the concentration of starting reactants. Under most favourable condition the dipeptide was synthesized. on the preparative scale in ca. 100% yield. As a result of immobilization (adsorption on the Sorsilen terephtalate support) the enzyme practically did not inactivate and may be used repeatedly.     

Enzymatic hydrolysis of starch in water-immiscible organic solvent,two-phase systems

Enzyme-catalyzed hydrolyzations of starch by α-amylase have been studied in various two-phase systems, consisting of water and a water-immiscible organic solvent. The hydrolytic conversion of soluble starch to malto-oligosaccharides by α-amylase was greatly accelerated in 10% (v/v) water content of water-dodecane two-phase systems. However, a rapid inactivation of the enzyme has been observed in these systems. Addition of surfactant to these systems, such as polyoxyethylene (20) sorbitan monopalmitate (Tween 60) or bis(2-ethylhexyl) sodium sulfosuccinate (AOT), was effective for the enzyme stability. Effects of enzyme immobilization on the stability of α-amylase, using Ca-alginate and chitosan beads, also have been studied. The stability of immobilized enzyme was clearly enhanced in a 5–10% (v/v) water content two-phase system, whereas the free enzyme was inactivated within 41 h, remaining at a relative activity of 47–76% after 41 h of treatment. Furthermore, scanning electron micrographs (SEM) were taken to observe the effect of the two-phase system on the hydrolysis of starch. Potato starch granules have been extremely swelled and burst out in the stirred 10% (v/v) water content system, which did not contain enzymes.