Cosolvency advantages

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. 

In our previous studies on chlorination of toluene we had found that solvent had an important effect on the selectivity. In particular, the use of diethyl ether as a cosolvent was advantageous for the production of a high proportion of the para-isomer (ref. 9). An experiment in which the amount of ether in a tetrachloromethane/diethyl ether solvent mixture was varied under otherwise identical reaction conditions (Ih reaction at 18°C with 1.04 molar equivalent of tert-butyl hypobromite) demonstrated that diethyl ether also had a marked influence on the selectivity of the bromination reaction (Fig. 6). There was also an effect on the yield of the reaction as performed under these standard conditions. As the... 

The Af-dansylated amino acid (e.g., glycine, leucine, proline) exhibits a yellow fluorescence. The sensitivity of detection for amino acids by this method is about 10 9 mol of amino acid. The advantage of this prodecure in comparison with that using dansyl chloride is the fact that it can be carried out in homogenous aqueous solution without addition of a cosolvent. 191... 

Use of cosolvent. Various cosolvents, such as acetone, ethanol, methanol, hexane, dichloromethane, and water, have been used for the removal of carotenoids using SC-CO2 extraction (Ollanketo and others 2001). All these cosolvents except water (only 2% of recovery) increased the carotenoid recovery. The use of vegetable oils such as hazelnut and canola oil as a cosolvent for the recovery of carotenoids from carrots and tomatoes have been reported (Sun and Temelli, 2006 Shi, 2001 Vasapollo and others 2004). For the extraction without cosolvent addition, the lycopene yield was below 10% for 2- to 5-hr extraction time, whereas in the presence of hazelnut oil, the lycopene yield increased to about 20% and 30% in 5 and 8 hr, respectively. The advantages of using vegetable oils as cosolvents are the higher extraction yield the elimination of organic solvent addition, which needs to be removed later and the enrichment of the oil with carotenoids that can be potentially used in a variety of product applications. 

According to researchers, cosolvent flushing has the following potential advantages ... 

The solubility of the components in the solvent must be sufficient. To improve the solubility, cosolvents can be used. Another possibility is the application of a two-phase system or an emulsion in the presence of phase-transfer catalysts. A two-phase system also has advantages in product isolation and continuous electrolysis procedures. A typical example is the synthesis of p-methoxy benzonitrile by anodic substitution of one methoxy group in 1,4-dimethoxybenzene by the cyanide ion (Eq. 22.21). The homogeneous cyanation system (acetonitrile, tetraethylammonium cyanide) [24] can be efficiently replaced by a phase-transfer system (dichloro-methane, water, sodium cyanide, tetrabutylammonium hydrogen sulfate) [71]. 

In general, from among the protic solvents, only liquid ammonia (the first used)1 is particularly useful, and is still used more than any other solvent despite the low temperature at which reactions have to be carried out (b.p. -33 °C) and the fact that solubilities of some aromatic substrates and salts (M+Nu-) are poor. Ammonia has the added advantage of being easily purified by distillation, being an ideal system for production of solvated electrons, and has very low reactivity with basic nucleophiles and radical anions, and aryl radicals. Also, poor solubilities can sometimes be ameliorated by use of cosolvents such as THF. In addition it can be used as a solvent for the in situ reductive generation of nucleophiles such as ArSe- and ArTe- ions, e.g. the formation of PhTe- from diphenyl ditelluride (equation 16).54 55... 

These redox chain reactions, which cycle iron(II) and iron(III), have advantages over methods that use stoichiometric quantities of oxidants because the hydroxymethyl radical is also a good reductant and, at high oxidant concentrations, it may be oxidized more rapidly than it adds to (72). The disadvantage of this type of reaction is that the initial radical is generated by a relatively non-selective hydrogen atom abstraction reaction. To be efficient, the H-donor must be used in large excess it is often a cosolvent. Nonetheless, this is a very practical method to prepare hydroxyalkylated and acylated heteroaromatic and related derivatives. 

Micelles as drug carriers provide many advantages. Comparing with cosolvent formulation, micellar formulation has less tendency of precipitation on dilution. They physically entrap sparingly... 

Even though use of cosolvents has its advantages in parenteral formulation, their use also brings up some additional issues that need to be addressed by the formulator. 

The extraction efficiency of supercritical fluids may be enhanced by mixing into it a small amount of a cosolvent such as acetone or methanol. Supercritical fluid extraction offers certain advantages over other extraction processes (1) it is relatively a fast process with greater extraction efficiency (2) sample concentration steps may be eliminated and (3) unlike LLE or Soxhlett extraction, a large amount of organic solvents is not required. 

Practical advantage of the method is that it does not require dry solvents. The resolving agent can be prepared by simple solution of DBTA monohydrate and half an equivalent amount of calcium oxide in hot 95 % ethyl alcohol. Crystallization of the diastereoisomeric coordination complex can be achieved by cooling and addition of cosolvents (e.g. acetone, toluene, ethyl acetate, etc.) or change ethyl alcohol to an ester type solvent. The enantiomers can be liberated from the crystalline complex by simple acidic workup procedure. [23]... 

A second approach takes full advantage of the retention gap by the addition of a small amount of cosolvent. The cosolvent is a higher-boiling solvent compared to the bulk eluent and serves to trap the volatiles while the bulk solvent evaporates. Thus, the sample is focused and the chromatography starts with sharp bands of analyte. The effects of the cosolvent and concurrent solvent evaporation have been reviewed [132], along with the minimum temperature need for concurrent solvent evaporation [133]. 

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