Solubilization cosolvency

An improved synthesis of 1 was developed by Moroni et al. (Table 3, entries 2 and 3), who coupled 19 and 20 (R = dodecyl) in the presence of PdCT, Cu(OAc)2, and triphenylphosphine in a triethylamine/ THF (Scheme 3) mixture. The authors claimed to have formed PPEs with a DP of approximately 150 and attributed the high molecular weight to the presence of THF as solubilizing cosolvent. Their claim with respect to molecular weights is unsubstanti-... 

Definition PEG ether of lanolin alcohol with avg. ethoxylation value of 5 Properties H LB 7.7 nonionic Toxicology TSCA listed Uses Emulsifier, emollient, stabilizer, solubilizer, cosolvent, wetting agent, dispersant, conditioner, vise, control agent for cosmetics, pharmaceuticals, creams and lotions bromo dye solvent Trade Name Synonyms Aqualose W5 [CrodaAA/estbrook] Fancol LA-5 t[Fanning... 

Uses Emulsifier, solubilizer, cosolvent, lubricant, dispersant, defoamer, corrosion inhibitor, wetting agent for cosmetics, pharmaceuticals, textiles, metalworking, agric., plastics, foods, water treatment defoamer for beet sugar and yeast processing defoamer in food-contact coatings in food-pkg. adhesives ... 

Uses Surfactant, emulsifier, solubilizer, cosolvent, thickener, emollient, opacifier, spreading agent, wetting agent, dispersant for cosmetics, pharmaceuticals, perfumes, foods, agric., plastics, other industries defoamer in food-contact paper/paperboard in resinous/polymeric food-contact coatings in resin-bonded filters for food contact in food-contact textiles... 

Uses Emulsifier, emollienL stabilizer, solubilizer, cosolvent, wetting agenL dispersant, conditioner, vise, control agent for cosmetics, creams and lotions, pharmaceuticals... 

Polymerization Solvent. Sulfolane can be used alone or in combination with a cosolvent as a polymerization solvent for polyureas, polysulfones, polysUoxanes, polyether polyols, polybenzimidazoles, polyphenylene ethers, poly(l,4-benzamide) (poly(imino-l,4-phenylenecarbonyl)), sUylated poly(amides), poly(arylene ether ketones), polythioamides, and poly(vinylnaphthalene/fumaronitrile) initiated by laser (134—144). Advantages of using sulfolane as a polymerization solvent include increased polymerization rate, ease of polymer purification, better solubilizing characteristics, and improved thermal stabUity. The increased polymerization rate has been attributed not only to an increase in the reaction temperature because of the higher boiling point of sulfolane, but also to a decrease in the activation energy of polymerization as a result of the contribution from the sulfonic group of the solvent. 

Surfactants and Dispersants. Castor od can be transformed from an od- to a water-soluble surfactant, depending on the moles of ethylene oxide added to its hydroxyl group. A 40 mole ethylene oxide adduct of castor od, known as PEG-40 castor od, is a surfactant that has cosolvent properties and is utilized as a fragrance solubilizer (118). Glycol hydroxystearate emulsifiers are formulated into shampoos to impart finer peadescence and give better stabdity than gylcol stearates (118) (see Hair preparation). 

Aromatic steroids are virtually insoluble in liquid ammonia and a cosolvent must be added to solubilize them or reduction will not occur. Ether, ethylene glycol dimethyl ether, dioxane and tetrahydrofuran have been used and, of these, tetrahydrofuran is the preferred solvent. Although dioxane is often a better solvent for steroids at room temperature, it freezes at 12° and its solvent effectiveness in ammonia is diminished. Tetrahydrofuran is infinitely miscible with liquid ammonia, but the addition of lithium to a 1 1 mixture causes the separation of two liquid phases, one blue and one colorless, together with the separation of a lithium-ammonia bronze phase. Thus tetrahydrofuran and lithium depress the solubilities of each other in ammonia. A tetrahydrofuran-ammonia mixture containing much over 50 % of tetrahydrofuran does not become blue when lithium is added. In general, a 1 1 ratio of ammonia to organic solvents represents a reasonable compromise between maximum solubility of steroid and dissolution of the metal with ionization. 

Soluble organic solvents have often been used as cosolvents to solubilize miscible organic substrates. Since organic compounds including solvents are possibly incorporated inside of the enzyme, they may affect the stereoselectivity of enzymatic reactions. For example, dimethyl sulfoxide (DMSO) (10%) enhance not only chemical yield but also enantioselectivity of yeast reduction. Thus, the poor yield of 23% with 80% ee was increased to 65% yield with >99% ee (Figure 8.20) [17]. 

Product recovery from reversed micellar solutions can often be attained by simple backextraction, by contacting with an aqueous solution having salt concentration and pH that disfavors protein solubilization, but this is not always a reliable method. Addition of cosolvents such as ethyl acetate or alcohols can lead to a disruption of the micelles and expulsion of the protein species, but this may also lead to protein denaturation. These additives must be removed by distillation, e.g., to enable reconstitution of the micellar phase. Temperature increases can similarly lead to product release as a concentrated aqueous solution. Removal of the water from the reversed micelles by molecular sieves or silica gel has also been found to cause a precipitation of the protein from the organic phase. 

Many research compounds are poorly soluble in water. When very lipophilic molecules precipitate in the donor wells, it is possible to filter the donor solution before the PAMPA sandwich is prepared. On occasion, the filtered donor solution contains such small amounts of the compound that determination of concentrations by UV spectrophotometry becomes impractical. One strategy to overcome the precipitation of the sample molecules in the donor wells is to add a cosolvent to the solutions (Section 7.4.4). It is a strategy of compromise and practicality. Although the cosolvent may solubilize the lipophilic solute molecule, the effect on transport may be subtle and not easy to predict. At least three mechanisms may cause Pe and membrane retention (%R) values to alter as a result of the cosolvent addition. To a varying extent, all three mechanisms may simultaneously contribute to the observed transport ... 

The most soluble gasoline compound is methyl tertiary-butyl ether (MTBE) (43,000 mg/L). In addition, MTBE in solution has a cosolvent effect, causing some of the other compounds in gasoline to solubilize at higher concentrations than they normally would in clean water. 

One potential risk that formulators run when using cosolvents as drug solubilizers is the possibility of vehicle toxicity. Each cosolvent is characterized by an acceptable concentration range, which cannot be exceeded without incurring biological damage. To avoid the requirement for in vivo testing, several in vitro models have been advanced to evaluate the relative safety of cosolvent excipients. The most useful in vitro procedure follows the hemolysis of red blood cells, which has been correlated with in vivo animal tests [87,88]. 

In dilute solutions, the solute will, on average, contact only one hydrated cosolvent molecule at a time, and the degree of solubilization should be a linear rather than a logarithmic function of cosolvent content. Thus, it is expected that the log-linear relationship between Sm andf. that applies at high cosolvent concentrations will become linear at low cosolvent levels due to a change in the mechanism of solubilization. If S is defined as solubility enhancement... 

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