Solvents water miscibility

C HjCla, PhCCla. Colourless liquid, b.p. 2I3-214" C. Insoluble in water, miscible with organic solvents. 

Worldwide demand for DMF in acryhc fiber production has held up better than in the United States. The high solubiUty of polyacrylonitrile in DMF, coupled with DMF s high water miscibility, makes it an attractive solvent for this appHcation. Its principal competition in this area comes from DMAC. 

Figure 4a represents interfacial polymerisation encapsulation processes in which shell formation occurs at the core material—continuous phase interface due to reactants in each phase diffusing and rapidly reacting there to produce a capsule shell (10,11). The continuous phase normally contains a dispersing agent in order to faciUtate formation of the dispersion. The dispersed core phase encapsulated can be water, or a water-immiscible solvent. The reactant(s) and coreactant(s) in such processes generally are various multihmctional acid chlorides, isocyanates, amines, and alcohols. For water-immiscible core materials, a multihmctional acid chloride, isocyanate or a combination of these reactants, is dissolved in the core and a multihmctional amine(s) or alcohol(s) is dissolved in the aqueous phase used to disperse the core material. For water or water-miscible core materials, the multihmctional amine(s) or alcohol(s) is dissolved in the core and a multihmctional acid chloride(s) or isocyanate(s) is dissolved in the continuous phase. Both cases have been used to produce capsules. 

In addition to these forms of water, several other official aqueous vehicles can be used. These are isotonic injections that can be sterilised, eg, sodium chloride. Ringer s, dextrose, dextrose and sodium chloride, and lactated Ringer s. Addition of water-miscible solvents such as ethanol or propylene glycol increases solubiUty and stabiUty. 

As solvents, the amyl alcohols are intermediate between hydrocarbon and the more water-miscible lower alcohol and ketone solvents. Eor example, they are good solvents and diluents for lacquers, hydrolytic fluids, dispersing agents in textile printing inks, industrial cleaning compounds, natural oils such as linseed and castor, synthetic resins such as alkyds, phenoHcs, urea —formaldehyde maleics, and adipates, and naturally occurring gums, such as shellac, paraffin waxes, rosin, and manila. In solvent mixtures they dissolve cellulose acetate, nitrocellulose, and ceUulosic ethers. 

In reversed-pViase chromatography (RPC), the mobile phase modulator is typically a water-miscible organic solvent, and the stationary phase is a hydrophobic adsorbent. In this case, the logarithm of solute retention factor is commonly found to be linearly related to the volume fraction of the organic solvent. 

If the column is contaminated with hydrophobic compounds, clean it with water-miscible organic solvents such as MeOH, CHjCN, or EtOH. Concentrations of 10-20% organic in water should be sufficient for cleaning. 

The choice of the anion ultimately intended to be an element of the ionic liquid is of particular importance. Perhaps more than any other single factor, it appears that the anion of the ionic liquid exercises a significant degree of control over the molecular solvents (water, ether, etc.) with which the IL will form two-phase systems. Nitrate salts, for example, are typically water-miscible while those of hexaflu-orophosphate are not those of tetrafluoroborate may or may not be, depending on the nature of the cation. Certain anions such as hexafluorophosphate are subject to hydrolysis at higher temperatures, while those such as bis(trifluoromethane)sulfonamide are not, but are extremely expensive. Additionally, the cation of the salt used to perform any anion metathesis is important. While salts of potassium, sodium, and silver are routinely used for this purpose, the use of ammonium salts in acetone is frequently the most convenient and least expensive approach. 

When water-miscible ionic liquids are used as solvents, and when the products are partly or totally soluble in these ionic liquids, the addition of polar solvents, such as water, in a separation step after the reaction can make the ionic liquid more hydrophilic and facilitate the separation of the products from the ionic liquid/water mixture (Table 5.3-2, case e). This concept has been developed by Union Carbide for the hydroformylation of higher alkenes catalyzed by Rh-sulfonated phosphine ligand in the N-methylpyrrolidone (NMP)/water system. Thanks to the presence of NMP, the reaction is performed in one homogeneous phase. After the reaction. 

When either the organic solvent or the ionic liquid is used as pure solvent, proper control over the water content, or rather the water activity, is of crucial importance, as a minimum amount is necessary to maintain the enzyme s activity. For ionic liquids, a reaction can be operated at constant water activity by use of the same methods as established for organic solvents [17]. [BMIM][PFg] or [BMIM][(CF3S02)2N], for example, may be used as pure solvents and in biphasic systems. Water-miscible ionic liquids, such as [BMIM][BF4] or [MMIM][MeS04], can be used in the second case. 

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