Solution biphasic

Fig. 12 Pn-4 (a, b) and Pn-8 (c, d) P-sheet variation measure by IR circles) and NMR triangles). 10 mg mL peptide solutions prepared in (a, c) D2O and (b, d) 130 mM NaCl in D2O. For Pii-4, I nematic gel, II flocculate, III nematic fluid, IV isotropic fluid. For Pn-8, I isotropic fluid, II biphasic solution. III nematic gel. Adapted from Carrick et al. [23]. Copyright 2007, with permission from Elsevier...

In summary, what we have found is that the combination of a thermomorphic system and a surfactant is very effective for the hydroformylation of 1-octene and 1-dodecene. We believe that although a 90 10 ethanol/water and heptane system becomes miscible at 70°C, the additional water in a 50 50 ethanol/water and heptane system raises the miscibility temperature to >100°C. When a surfactant is added, the miscibility temperature is lowered and the biphasic solution becomes monophasic below the reaction temperature, resulting in good reaction rates. In addition, the presence of the surfactant also enhances the selectivity compared to the completely homogeneous system from 1.8 to 5.3 L/B... 

Various other biphasic solutions to the separation problem are considered in other chapters of this book, but an especially attractive alternative was introduced by Horvath and co-workers in 1994.[1] He coined the term catalysis in the fluorous biphase and the process uses the temperature dependent miscibility of fluorinated solvents (organic solvents in which most or all of the hydrogen atoms have been replaced by fluorine atoms) with normal organic solvents, to provide a possible answer to the biphasic hydroformylation of long-chain alkenes. At temperatures close to the operating temperature of many catalytic reactions (60-120°C), the fluorous and organic solvents mix, but at temperatures near ambient they phase separate cleanly. Since that time, many other reactions have been demonstrated under fluorous biphasic conditions and these form the basis of this chapter. The subject has been comprehensively reviewed, [2-6] so this chapter gives an overview and finishes with some process considerations. 

In general, it can be concluded, that although a large scale biphasic solution process for hydrodesulfurization and hydrodenitrogenation is not likely to come soon, there are promising results in homogeneous catalysis which can lead to constmction of such processes in the future. 

The mixture becomes a pale orange, biphasic solution. This mixture becomes red if the addition of triethylamine is too fast. 

In 2004, excellent yields of hydroperoxides 91 and 92 were obtained (>95%) in the photooxidation of racemic acid 90 (Scheme 11.17) [96]. The diastereoselectivity of the photooxidation favored the trans-configured products due to the anti-directing effect of the protonated carboxylic acid group. Regioselectivity favored the formation of 92 over 91. Pyridine helped to accelerate the deprotonation of the CH next to COOH of 90, affording 92, and also suppressed the formation of aromatic compounds which otherwise would take place in the absence of pyridine. A great many studies of ene reactions have been conducted in organic solvents [97-101] or aqueous media [102-106] one such report appeared which used a fluorous biphasic solution [107]. 

Qualitatively, the same effect has been observed in ternary solutions of p- PODZ, PA-6 and sulfuric acid [104]. At room temperature the quiescent system displays phase separation above 14% of total polymer concentration. Above the critical concentration shearing of initially biphasic solutions led to transparent one-phase systems. After cessation of the shear stress the biphasic morphologies recovered. 

The Step 5 product (42.11 mmol) was added to 198 ml THF/r-butyl alcohol/2-methyl-2-butene, 1 1 1.3, cooled to 0°C, then treated with sodium chlorite (331.1 mmol), and sodium dihydrogen phosphate monohydrate (256.7 mmol) dissolved in 102 ml water. The biphasic solution was stirred for 10 minutes at 0°C and then 1 hour at ambient temperature and was then concentrated. The residue was diluted with 200 ml water and the pH adjusted to 3 using saturated NaHC03 solution and 1M HC1. The aqueous solution was extracted four times with THF/CH2C12, 1 2, dried with MgS04, and concentrated. The residue was purified by trituration with diethyl ether and the product isolated in 88% yield as a white solid. 

RUO2 (5 mol) was added to the product from Step 4 (2.93 mmol) in a biphase solution of 180 ml water, 60 ml acetonitrile and 120 ml CCI4 containing NaI04 (116 mmol) and the mixture stirred vigorously 5 days. The volatile solvents were removed, the mixture extracted 3 times with 150 ml EtOAc, dried, and the product isolated in 96% yield. H-and F-NMR and elemental analysis data supplied. 

Inductive activation of the amide by the adjacent fluorine atom allows for the basic hydrolysis of the amide bond under relatively mild conditions (warming to 75 °C in a biphasic solution of 2 N sodium hydroxide in a 2 2 1 mixture of water, terf-butyl alcohol, and methanol) to form carboxylic acids with high enantiomeric excess (eq 26). ... 

To a 20 mL flask was added 2.5 g of (R,S)-2-ethoxycarbonyl-3,6-dihydro-2H-pyran, followed by 7 mL of 0.2 M pH 7.5 phosphate buffer and 2 mL of Bacillus lentus protease-III solution (approximately 5% solution of the protein). The biphasic solution was stirred at room temperature (23 °C) using a magnetic stirrer. The pH was checked at 0.5 hour intervals and readjusted to 7.5 by the drop-wise addition of 1 N NaOH (approximately 7 mL were required over the complete reaction). The progress of the reaction was monitored by chiral gas chromatography. After 5 hours, the enantiomeric purity of the unreacted ester was >99% and the reaction was stopped by the addition of 10 mL of MTBE. The pH of the aqueous phase was adjusted to 8.5 and the mixture was transferred into a separatory funnel. The aqueous phase was extracted twice with 20 mL of MTBE and the combined organic layers were extracted once with saturated sodium bicarbonate (10 mL), followed by saturated sodium chloride solution (10 mL), and the organic... 

Suspend 4-f-butylcalix[4]arene (1.5 g, 2.0 mmol) and phenol (0.28 g, 3.0 mmol) in toluene (30 mL) in a two-necked round-bottomed flask (125 mL) with an inlet providing a flux of inert gas and an outlet fitted with a calcium chloride guard tube. Add anhydrous aluminium trichloride (1.5 g, 11 mmol), which clarifies the suspension slightly, and stir for 4h. During this time the mixture turns from colourless to yellow then orange. A red oil may be observed to separate. After 4 h, add hydrochloric acid (65 mL of a 1m aqueous solution) and continue to stir vigorously for a further 1 h. Ensure that all the sticky red oil is removed from the sides of the vessel and is stirred into the biphasic solution. It may be necessary to use a spatula to free this material. The upper aromatic layer will turn yellow and solids will precipitate out within it. Once all the oil has been stirred to yield a powdery product, leave the mixture to settle for 20 min. Separate the upper organic... 

Polyl/J-phenylene terephthalamide)/ PA or PARA, and PEKK or PAN biphasic solution in sulfuric acid, spun, coagulated, stretched into PPD-T fibrils Coburn Yang, 1994... 

Poly(acrylic acid) with Rh-phosphine complexes =1.04 HP Hydroformylation of olefins (gas phase and biphasic solution) Phase separation (r) [144]... 

Supercritical fluid extraction with CO2 has shown that a wide variety of solutes can be extracted from ILs with the solutes being recovered without IL contamination [9,45,46]. This is accomplished as CO2 dissolves in the solvent mixture to facilitate extraction, but the IL does not dissolve in CO2, so pure product can be recovered. In addition, IL/CO2 biphasic solutions have been used for a variety of homogeneously catalyzed reactions, as well as for extraction and recovery of organic solutes. Interestingly, the CO2/IL system remains two distinct phases, even under pressures up to 400 bar [46]. 

Wasserscheid et al. found that aluminum chloride dissolves in triflimide ionic liquids to form biphasic solutions. These solutions can be used to promote the Friedel-Crafts acylation reaction, and an interesting variant is the carbonylation of toluene with carbon monoxide (Scheme 5.2-28) [72]. The ionic liquid can be recycled, but the aluminum chloride is lost when the reaction is worked up. 

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