Solvents phase transfer

Extraction of protein from aqueous solution by surfactant-containing lipophilic organic solvent (phase transfer method, or equivalently, w/o-ME-based liquid-liquid extracting, LEE). 

Phase transfer catalysts can be used to increase the solubility of reactants in the phase where the reaction takes place. Usually these catalysts are organophilic salts that pair with anionic reactants to increase their solubility in organic solvents. Phase transfer catalysis is described in more detail in Chapter 5. 

The fundamental mechanisms for solute mass transfer in liquid-liquid extraction involve molecular diffusion driven by a deviation from equilibrium. When a liquid feed is contacted with a liquid solvent, solute transfers from the interior of the feed phase across a liquid-liquid interface into the interior of the solvent phase. Transfer of solute will continue until the solute s chemical potential is the same in both phases and equilibrium is achieved. 

Dibromoethane has most frequently been used as the nucleophile, though occasionally E2-dichloroethane or l-bromo-2-chloroethane give better yields. The reaction is induced by a variety of bases and is performed in polar solvents. Phase-transfer conditions can also be successfully applied. Generally, nucleophiles obtained from doubly activated methylene compounds give the best results, though monoactivated nucleophiles may also react with 1,2-... 

The reason could be that alcohol and ether are extracted into the water phase when the organic phase is mixed with water, which results in a competitive adsorption with the surfactant and a decrease of the transfer ability of the sol particles into benzene. When xylene or ligarine is used as solvent, phase transfer also failed, although the properties of the former is similar to benzene. The phase transfer is successful for kerosene, but the filtering to remove kerosene and residual water would be very difficult. In addition, the formation of colloidal matter and oxidation-reduction reaction between copper ion and kerosene is possible when continuously heating. Thus, kerosene is not a suitable solvent for the system to be studied. 

The reaction is somewhat slow, even in aprotic dipolar solvents. The most reliable procedures involve heating the appropriate halide with sodium azide in dimethyl sulfoxide" or dimethylformamide." Alkyl azides can be prepared by reaction of sodium azide with iodides using high-boiling alcohols as the solvent." Phase transfer... 

Simplest examples are prepared by the cyclic oligomerization of ethylene oxide. They act as complexing agents which solubilize alkali metal ions in non-polar solvents, complex alkaline earth cations, transition metal cations and ammonium cations, e.g. 12—crown —4 is specific for the lithium cation. Used in phase-transfer chemistry. ... 

Triton B Trade name for benzyltrimethyl-ammonium hydroxide usually as a 40% solution in methanol. A strong base, soluble in many solvents used as a catalyst. See phase transfer chemistry. 

The benzoic acid derivative 457 is formed by the carbonylation of iodoben-zene in aqueous DMF (1 1) without using a phosphine ligand at room temperature and 1 atm[311]. As optimum conditions for the technical synthesis of the anthranilic acid derivative 458, it has been found that A-acetyl protection, which has a chelating effect, is important[312]. Phase-transfer catalysis is combined with the Pd-catalyzed carbonylation of halides[3l3]. Carbonylation of 1,1-dibromoalkenes in the presence of a phase-transfer catalyst gives the gem-inal dicarboxylic acid 459. Use of a polar solvent is important[314]. Interestingly, addition of trimethylsilyl chloride (2 equiv.) increased yield of the lactone 460 remarkabiy[3l5]. Formate esters as a CO source and NaOR are used for the carbonylation of aryl iodides under a nitrogen atmosphere without using CO[316]. Chlorobenzene coordinated by Cr(CO)j is carbonylated with ethyl formate[3l7]. 

Nevertheless, they are stable to standard work-up and purification methods. The benzenesulfonyl group can be introduced using base and an aprotic solvent[3] or under phase transfer conditions[4], Table 9.2 gives some representative examples of acylation and sulfonylations. 

Phase transfer catalysis succeeds for two reasons First it provides a mechanism for introducing an anion into the medium that contains the reactive substrate More important the anion is introduced m a weakly solvated highly reactive state You ve already seen phase transfer catalysis m another form m Section 16 4 where the metal complexmg properties of crown ethers were described Crown ethers permit metal salts to dissolve m nonpolar solvents by surrounding the cation with a lipophilic cloak leav mg the anion free to react without the encumbrance of strong solvation forces... 

Quaternary ammonium salts compounds of the type R4N" X find application m a technique called phase transfer catalysis A small amount of a quaternary ammonium salt promotes the transfer of an anion from aqueous solution where it is highly solvated to an organic solvent where it is much less solvated and much more reactive... 

Fig. 9. Membrane extraction where the solvent phase is represented by hatched lines and the arrows show the direction of mass transfer, (a) Spherical film (b) emulsion globule where the strip solution is represented by circles and (c) hoUow fiber support.

The alkene is allowed to react at low temperatures with a mixture of aqueous hydrogen peroxide, base, and a co-solvent to give a low conversion of the alkene (29). These conditions permit reaction of the water-insoluble alkene and minimise the subsequent ionic reactions of the epoxide product. Phase-transfer techniques have been employed (30). A variation of this scheme using a peroxycarbimic acid has been reported (31). 

A2iridines (X = H) can be alkylated on the nitrogen, with retention of the three-membered ring, by reaction with aUphatic and aromatic haUdes in the presence of base (2,154). The reaction can also be carried out, in some cases with very good yields, under phase-transfer conditions using 30% NaOH and optionally an organic solvent (155). If the haUdes do not react readily, the alkaU metal salts (X = Na) of the corresponding ayiridine can be used (156—158) to form, for example, triethyleneiminemethane [23974-29-0].. 

Although phosphine [7803-51-2] was discovered over 200 years ago ia 1783 by the French chemist Gingembre, derivatives of this toxic and pyrophoric gas were not manufactured on an industrial scale until the mid- to late 1970s. Commercial production was only possible after the development of practical, economic processes for phosphine manufacture which were patented in 1961 (1) and 1962 (2). This article describes both of these processes briefly but more focus is given to the preparation of a number of novel phosphine derivatives used in a wide variety of important commercial appHcations, for example, as flame retardants (qv), flotation collectors, biocides, solvent extraction reagents, phase-transfer catalysts, and uv photoinitiators. 

A method for the polymerization of polysulfones in nondipolar aprotic solvents has been developed and reported (9,10). The method reUes on phase-transfer catalysis. Polysulfone is made in chlorobenzene as solvent with (2.2.2)cryptand as catalyst (9). Less reactive crown ethers require dichlorobenzene as solvent (10). High molecular weight polyphenylsulfone can also be made by this route in dichlorobenzene however, only low molecular weight PES is achievable by this method. Cross-linked polystyrene-bound (2.2.2)cryptand is found to be effective in these polymerizations which allow simple recovery and reuse of the catalyst. 

Pha.se-Tra.nsfer Ca.ta.lysts, Many quaternaries have been used as phase-transfer catalysts. A phase-transfer catalyst (PTC) increases the rate of reaction between reactants in different solvent phases. Usually, water is one phase and a water-iminiscible organic solvent is the other. An extensive amount has been pubHshed on the subject of phase-transfer catalysts (233). Both the industrial appHcations in commercial manufacturing processes (243) and their synthesis (244) have been reviewed. Common quaternaries employed as phase-transfer agents include benzyltriethylammonium chloride [56-37-17, tetrabutylammonium bromide [1643-19-2] tributylmethylammonium chloride [56375-79-2] and hexadecylpyridinium chloride [123-03-5]. 

Other commercial naphthalene-based sulfonic acids, such as dinonylnaphthalene sulfonic acid, are used as phase-transfer catalysts and acid reaction catalysts in organic solvents (71). Dinonylnaphthalene sulfonic acid is an example of a water-insoluble synthetic sulfonic acid. 

Removing an analyte from a matrix using supercritical fluid extraction (SEE) requires knowledge about the solubiUty of the solute, the rate of transfer of the solute from the soHd to the solvent phase, and interaction of the solvent phase with the matrix (36). These factors collectively control the effectiveness of the SEE process, if not of the extraction process in general. The range of samples for which SEE has been appHed continues to broaden. Apphcations have been in the environment, food, and polymers (37). 

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