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Polyethylene glycol solvent

It is observed that the most efficient ligands are crown ethers and criptates, followed by aprotic dipolar solvents, polyethylene glycols, glymes and finally bidentate amines. [Pg.85]

Type of organic solvent Determines the strength and possibility of organogelation. Polar solvent increases the cross-sectional area of the spherical micelles upon incorporation. Nonaqueous solvent (polyethylene glycol) replaces water of the bacterial cellulose hydrogel without destroying it s shape. ... [Pg.707]

LiAlH is soluble in ethers, 35-40 g/100 g diethyl ether at 25°C. Solubihty in THF, the other common solvent for LiAlH, is 13 g/100 g at 25°C. Polyethylene glycol diaLkyl ethers are also good solvents. [Pg.305]

The solvent can be tailored to provide selective acid gas removal based on the Hquid—gas solubiHties. For example, the Selexol process, Hcensed by Union Carbide Corporation, uses the dimethyl ether of polyethylene glycol (DMPEG) to provide high hydrogen sulfide selectivity. The solubiHty of hydrogen sulfide in DMPEG is 8—10 times that of carbon dioxide. [Pg.212]

In contrast to phosphorus esters, sulfur esters are usually cleaved at the carbon-oxygen bond with carbon-fluorine bond formation Cleavage of esteri nf methanesulfonic acid, p-toluenesidfonic acid, and especially trifluoromethane-sulfonic acid (tnflic acid) by fluoride ion is the most widely used method for the conversion of hydroxy compounds to fluoro derivatives Potassium fluoride, triethylamine trihydrofluoride, and tetrabutylammonium fluoride are common sources of the fluoride ion For the cleavage of a variety of alkyl mesylates and tosylates with potassium fluoride, polyethylene glycol 400 is a solvent of choice, the yields are limited by solvolysis of the leaving group by the solvent, but this phenomenon is controlled by bulky substituents, either in the sulfonic acid part or in the alcohol part of the ester [42] (equation 29)... [Pg.211]

The solubility of latex in water can be improved by replacing the solvent used in the system. Initially, the water is removed and than a hydrophobic organic solvent is replaced by a hydrophilic solvent, which has a boiling point above 100 C. This last solvent can be ethylene glycol, diethyl ether of diethylene glycol, monoethyl ether of ethylene glycol, or polyethylene glycols. This treatment results in a pastelike composition that can be easily mixed with water and used as a final product. [Pg.69]

Important processes commercially used are the Selexol, the Sulfinol, and the Rectisol processes. In these processes, no chemical reaction occurs between the acid gas and the solvent. The solvent, or absorbent, is a liquid that selectively absorbs the acid gases and leaves out the hydrocarbons. In the Selexol process for example, the solvent is dimethyl ether of polyethylene glycol. Raw natural gas passes countercurrently to the descending solvent. When the solvent becomes saturated with the acid gases, the pressure is reduced, and hydrogen sulfide and carbon dioxide are desorbed. The solvent is then recycled to the absorption tower. Figure 1-1 shows the Selexol process. ... [Pg.3]

The simplest way to prepare a biocatalyst for use in organic solvents and, at the same time, to adjust key parameters, such as pH, is its lyophilization or precipitation from aqueous solutions. These preparations, however, can undergo substrate diffusion limitations or prevent enzyme-substrate interaction because of protein-protein stacking. Enzyme lyophilization in the presence of lyoprotectants (polyethylene glycol, various sugars), ligands, and salts have often yielded preparations that are markedly more active than those obtained in the absence of additives [19]. Besides that, the addition of these ligands can also affect enzyme selectivity as follows. [Pg.9]

Adsorption on solid matrices, which improves (at optimal protein/support ratios) enzyme dispersion, reduces diffusion limitations and favors substrate access to individual enzyme molecules. Immobilized lipases with excellent activity and stability were obtained by entrapping the enzymes in hydrophobic sol-gel materials [20]. Finally, in order to minimize substrate diffusion limitations and maximize enzyme dispersion, various approaches have been attempted to solubilize the biocatalysts in organic solvents. The most widespread method is the one based on the covalent linking of the amphiphilic polymer polyethylene glycol (PEG) to enzyme molecules [21]. [Pg.9]

The precipitation method of separation involves the addition of salts such as ammonium sulfate or solvents such as polyethylene glycol to the reagent mixture to cause precipitation of the large molecular weight bound species. These methods of precipitation lack specificity and work well only when there is a large difference between the molecular weight of the material being measured and that of the bound complex of it. [Pg.60]

It is possible to synthesize cobalt complexes which are soluble in polyethylene glycols and not in. solvents like hexane, hexene, heptenal etc. Ritter et al. (1996) have reported the oxo reaction of 1-hexene in such a system. [Pg.142]

The development of catalysts for the efficient oxidation of catechol and its derivatives in water is topic of ongoing work in this laboratory. Towards this end, polyethylene glycol side-chains were incorporated in a pentadentate salen ligand to enhance the water solubility of the complexes derived thereof. A dinuclear copper(II) complex is found to catalyze the oxidation of 3,5-di-tert.-butylcatechol into 3,5-di-tert-butyl-o-benzoquinone more than twice as fast in aqueous organic solution as in purely organic solvents (ly,at/knon= 140,000). Preliminary data are discussed. [Pg.473]

In our ongoing efforts to develop oxidation catalysts that are functional in water as environmentally berrign solvent, we synthesized a water-soluble pentadentate salen ligand with polyethylene glycol side chairts (8). After coordination of copper(II) ions to the salen ligand, a dinuclear copper(II) complex is obtained that is soluble in water, methanol and mixtures of both solvents. The aerobic oxidation of 3,5-di-tert.-butylcatechol (DTBC) into 3,5-di-terr.-butylqitinone (DTBQ) was used as a model reaction to determine the catalytically active species and initial data on its catalytic activity in 80% methanol. [Pg.473]

In this type of reaction the active drug undergoes decomposition following reaction with the solvent present. Usually the solvent is water, but sometimes the reaction may involve pharmaceutical cosolvents such as ethyl alcohol or polyethylene glycol. These solvents can act as nucleophiles, attacking the electropositive centers in drug molecules. The most common solvolysis reactions encountered in pharmaceuticals are those involving labile carbonyl compounds such as esters, lactones, and lactams (Table 1). [Pg.147]

Glycerin, propylene glycol, and polyethylene glycol thickened with carboxyvinyl polymers (Carboxamer NF) provide organic solvent bases. Consistencies ranging from soft jelly to peanut butter can be achieved. [Pg.726]

Wang, P., Woodward, C.A., and Kaufman, E.N., Polyethylene glycol)-modified ligninase enhances pentachlorophenol biodegradation in water-solvent mixtures, Biotechnol. Bioeng., 64, 290-297, 1999. [Pg.686]


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See also in sourсe #XX -- [ Pg.286 ]

See also in sourсe #XX -- [ Pg.545 ]




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