Conventional immiscible

For the separation of immiscible liquids a small separating funnel of the conventional type should be used whenever practicable, a pear-shaped funnel (Fig. 16, p. 35) of 5-10 ml. capacity being particularly... 

In conventional solvent extraction, a solute is partitioned between two immiscible solvents. Here, used as an... 

Room temperature ionic liquids (RTILs), such as those based on A,A-dialkylimidazolium ions, are gaining importance (Bradley, 1999). The ionic liquids do not evaporate easily and thus there are no noxious fumes. They are also non-inflammable. Ionic liquids dissolve catalysts that are insoluble in conventional organic chemicals. IFP France has developed these solvents for dimerization, hydrogenation, isomerization, and hydroformylation reactions without conventional solvents. For butene dimerization a commercial process exists. RTILs form biphasic systems with the catalyst in the RTIL phase, which is immiscible with the reactants and products. This system is capable of being extended to a list of organometallic catalysts. Industrial Friedel-Crafts reactions, such as acylations, have been conducted and a fragrance molecule tra.seolide has been produced in 99% yield (Bradley, 1999). 

Counter-current chromatography using two immiscible liquid phases rather than a conventional solid phase ligand support allows chromatographic quality separations to be... 

Lipophilicity is a molecular property expressing the relative affinity of solutes for an aqueous phase and an organic, water-immiscible solvent. As such, lipophilicity encodes most of the intermolecular forces that can take place between a solute and a solvent, and represents the affinity of a molecule for a lipophilic environment. This parameter is commonly measured by its distribution behavior in a biphasic system, described by the partition coefficient of the species X, P. Thermodynamically, is defined as a constant relating the activity of a solute in two immiscible phases at equilibrium [111,112]. By convention, P is given with the organic phase as numerator, so that a positive value for log P reflects a preference for the lipid phase ... 

The introduction of a third phase - the membrane phase - between the two conventional phases (i.e., the aqueous and the organic phases) helps in overcoming many of the problems of solvent extraction. The membrane phase is a thin film, immiscible with the aque-... 

Inverse emulsification A solution of the polymer within a volatile, water-immiscible organic solvent (or mixture of solvents) or a polymer melt is compounded with a long-chain fatty acid (e.g., oleic acid) using conventional rubbermixing equipment and mixed slowly with a dilute aqueous phase to give a W/O emulsion,... 

As with classical multiphase catalysis, the organometallic catalyst is retained here in a liquid phase that is immiscible with the second phase containing substrates and/or products. For hydrogenation, the liquid/SCF system is always biphasic, whereas conventional systems are usually triphasic (liquid-1 /liquid-2/ H2). The liquid phase must provide a stable environment for the organometallic catalyst and should be insoluble in the SCF phase. Water, ILs and PEG have been used successfully for this purpose, together with scC02 as the mobile phase. Again, the products must not be too polar in order to be effectively extracted if C02 is used as the SCF. 

In Fig. 1.2, phase transformations are pnt into their context of physical processes used for separation of mixtures of chemical compounds. However, the figure has been drawn asymmetrically in that two Uqnids (I and II) are indicated. Most people are familiar with several organic Uqnids, Uke kerosene, ether, benzene, etc., that are only partially miscible with water. This lack of miscibility allows an equilibrium between two liquids that are separated from each other by a common phase boundary. Thus the conventional physical system of three phases (gas, liquid, and solid, counting all solid phases as one), which ordinarily are available to all chemists, is expanded to four phases when two immiscible liquids are involved. This can be of great advantage, as will be seen when reading this book. 

The liquid liquid partition chromatography (LLPQ method involves a stationary liquid phase that is more or less immobilized on a solid support, and a mobile liquid phase. The analyte is therefore distributed between the two liquid phases. In conventional LLPC systems, the stationary liquid phase is usually a polar solvent and the mobile liquid phase is an essentially water-immiscible organic solvent. On the other hand, in reversed-phase chromatography (RPQ, the stationary liquid is usually a hydrophobic... 

Nondispersive solvent extraction is a novel configuration of the conventional solvent extraction process. The term nondispersive solvent extraction arises from the fact that instead of producing a drop dispersion of one phase in the other, the phases are contacted using porous membrane modules. The module membrane separates two of the immiscible phases, one of which impregnates the membrane, thus bringing the liquid-liquid interface to one side of the membrane. This process differs from the supported liquid membrane in that the liquid impregnating the membrane is also the bulk phase at one side of the porous membrane, thus reducing the number of liquid-liquid interfaces between the bulk phases to just one. 

The incorporation of more inorganic appendages into TSIL cations has also been achieved through the use of l-(3-aminopropyl)imidazole. Phosphoramide groups are readily synthesized by treatment of phosphorous(V) oxyhahdes with primary or secondary amines. In just such an approach, l-(3-aminopropyl)imidazole was allowed to react with commerdaUy available (C H5)2POCl2 in dichloromethane. After isolation, the resulting phosphoramide was then quaternized at the imidazole N(3) position by treatment with ethyl iodide (Scheme 2.3-2). The viscous, oily product was found to mix readily with more conventional ionic Hquids such as [HMIM][PF ], yielding a more tractable material. This particular TSIL has been used to extract a number of actinide elements from water. Similarly, the thiourea-appended TSILs discussed earlier have been used for the extraction of Hg and Cd from IL-immiscible aqueous phases. 

Among the separation techniques, liquid-liquid (solvent) extraction is one of the best-known, well-established, versatile, and easy to use. However, traditional extraction employs conventional organic solvents immiscible with water, which are typically volatile, flammable, and health hazardous. This makes extraction inappropriate for modern and future environmental-friendly technologies and analysis processes. Another problem with conventional solvents is that their number is rather limited, so it may be difficult to find fhe solvenf ideally suifed for a particular application (even considering solvent mixtures). 

Additionally, ILs may serve as a convenient medium for analysis affer exfracfion. For example, fheir ionic nature opens an exciting opportunity of direcf elecfrochemical analysis of the extract, impossible for mosf of fhe conventional wafer-immiscible solvents. 

Here E is the solute excess molar refractivity, S is the solute dipolarity/ polarizability A and B are the overall or summation hydrogen-bond acidity and basicity, respectively and V is the McGowan characteristic volume lower-case letters stand for respective coefficients which are characteristic of the solvent, c is the constant. By help of sfafisfical methods like the principal component analysis and nonlinear mapping, the authors determined the mathematical distance (i.e., measure of dissimilarify) from an IL fo seven conventional solvents immiscible with water. It appears that the closest to the IL conventional solvent is 1-octanol. Even more close to IL is an aqueous biphasic system based on PEG-200 and ammonium sulfate (and even closer are ethylene glycol and trifluoroethanol, as calculated for hypofhefical water-solvenf sysfems involving fhese solvenfs). 

The above consideration of the similarity and dissimilarity of ILs and conventional extraction solvents ignores one particularly striking feature of ILs. In sharp contrast to common solvents immiscible with water, ILs are capable of ion exchange. We exemplify this very important ability by considering the extraction of amino acids on the basis of our work [24],... 

Intermolecular forces also play an important role in determining the compatibility of two or more polymers in a polymer blend or polymer alloy. Although the distinction between a polymer blend and a polymer alloy is still the subject of some debate, we will use the convention that a polymer alloy is a single-phase, homogeneous material (much as for a metal), whereas a blend has two or more distinct phases as a result of polymer-polymer immiscibility (cf. Section 2.3.3). In general, polymers are... 

As in the case of LCP/conventional polymer blending, little data exists on the blending of LCPs of different inherent chain architecture or mesophase symmetry. Publications from the laboratories of Ringsdorf [80] and Finkelmann [81] show phase separation in blends of sidechain nematics with other similar polymers or small molecule analogs. It is now established that, in contrast to the behavior of low molecular weight LCs, LCPs are often immiscible. 

The electrodes used in conventional polarography and voltammetry are electronic conductors such as metals, carbons or semiconductors. In an electrode reaction, an electron transfer occurs at the electrode/solution interface. Recently, however, it has become possible to measure both ion transfer and electron transfer at the interface between two immiscible electrolyte solutions (ITIES) by means of polarography and voltammetry [16]. Typical examples of the immiscible liquid-liquid interface are water/nitrobenzene (NB) and water/l,2-dichloroethane (DCE). 

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