Phase inverse

Substituting for the corrected retention volumes in equation (9) for inverse phase system,... 

Poly(VPGVG) (Fig. 6) has been smdied most thoroughly and it was shown that it exhibits an inverse phase transition. The biopolymer undergoes phase separation from solution upon increasing temperature, resulting in a p-spiral structure and simultaneous release of water molecules associated with the polymer chain (Fig. 7). 

Fig. 9 Purification of ELPs by ITC is based on the reversible inverse phase transition. Le/i Protein purification via direct ELP fusions. A soluble ELP fused to a target protein becomes reversibly insoluble upon increasing temperature above 7,. Center Protein purification via ELP coaggregation. An excess of free ELPs enhances the aggregation of trace quantities of ELP-fusions. Right Purification via ELP-mediated affinity capture (EMAC). ELPs are fused to capture proteins, which bind specifically and reversibly to a target protein. This target protein can then be aggregated at temperatures above the T,. Adapted from [38] with permission from Elsevier, copyright 2010...

Oxymercuration/demercuration provides a milder alternative for the conventional acid-catalyzed hydration of alkenes. The reaction also provides the Markovnikov regiochemistry for unsymmetrical alkenes.33 Interestingly, an enantioselective/inverse phase-transfer catalysis (IPTC) reaction for the Markovnikov hydration of double bonds by an oxymercuration-demercuration reaction with cyclodextrins as catalysts was recently reported.34 Relative to the more common phase-transfer... 

Alternatively, the Sn2 nucleophilic substitution reaction between alcohols (phenols) and organic halides under basic conditions is the classical Williamson ether synthesis. Recently, it was found that water-soluble calix[n]arenes (n = 4, 6, 8) containing trimethylammonium groups on the upper rim (e.g., calix[4]arene 5.2) were inverse phase-transfer catalysts for alkylation of alcohols and phenols with alkyl halides in aqueous NaOH solution to give the corresponding alkylated products in good-to-high yields.56... 

The water-soluble calix[n]arenes 6.3 (n = 4, 6 and 8) containing trimethylammonium groups act as efficient inverse phase-transfer catalysts in the nucleophilic substitution reaction of alkyl and arylalkyl halides with nucleophiles in water (Eq. 6.19).40 In the presence of various surfactants (cationic, zwitterionic and anionic), the reactions of different halides and ketones show that the amount of ketone alkylation is much higher and that the reactions are faster in the presence than in the absence of surfactant aggregates.41 The hydrolysis of the halide is minimized in the presence of cationic or zwitterionic surfactants. 

Reduction of carbonyl compounds can be carried out in an aqueous medium by various reducing reagents. Among these reagents, sodium borohydride is the most frequently used. The reduction of carbonyl compounds by sodium borohydride can also use phase-transfer catalysts (Eq. 8.4),10 inverse phase-transfer catalysts,11 or polyvinylpyridines12... 

Compared with esters, acid halides and anhydrides are more reactive and are hydrolyzed more readily. It is interesting to note that there is a substantial lifetime for these acid derivatives in aqueous media. Acid halides dissolved in PhCl or in PhBr shaken at a constant rate with water shows that hydrolysis occurs at the boundary between the two liquid phases.35 The reaction of benzoyl chloride (PhCOCl) and benzoate ion with pyridine A-oxide (PNO) as the inverse phase-transfer catalyst yields both the substitution product (benzoic anhydride) and the... 

Fig. 1 Morphologies of diblock copolymers cubic packed spheres (S), hexagonal packed cylinders (C or Hex), double gyroid (G or Gyr), and lamellae (L or Lam). Inverse phases not shown. From [8], Copyright 2000 Wiley...

Monflier and co-workers recently described a new approach based on the use of chemically modified /3-cyclodextrins to peform efficiently the functionalization of water-insoluble olefins in a two-phase system. These compounds behave as inverse phase transfer catalysis, i.e., they transfer olefins into the aqueous phase via the formation of inclusion complexes.322... 

In order to keep the mild conditions, hydroxycarbonylation has been performed in biphasic media, maintaining the catalyst in the aqueous phase thanks to water-soluble mono- or diphosphine ligands. In the presence of the sodium salt of trisulfonated triphenylphosphine (TPPTS), palladium was shown to carbonylate efficiently acrylic ester [19], propene and light alkenes [20,21] in acidic media. For heavy alkenes the reduced activity due to the mass transfer problems between the aqueous and organic phases can be overcome by introducing an inverse phase transfer agent, and particularly dimeihyl-/-i-cyclodextrin [22,23]. Moreover, a dicationic palladium center coordinated by the bidentate diphosphine ligand 2,7-bis(sulfonato)xantphos (Fig. 2) catalyzes, in the presence of tolylsulfonic acid for stability reasons, the hydroxycarbonylation of ethylene, propene and styrene and provides a ca. 0.34 0.66 molar ratio for the two linear and branched acids [24],... 

Cyclodextrins are often used as inverse phase transfer catalysts [11-14]. They are able to intercalate hydrophobic substances and to transport them into a polar phase like water, where the reaction takes place. To study the influence of cyclodextrins on the isomerizing hydroformylation of frans-4-octene in the biphasic solvent system propylene carbonate/dodecane, the concentration of methylated /3-cyclodextrin was varied from 0.2 up to 2.0 mol.-% relative to the substrate frans-4-octene [24]. The results are given in Table 7. 

One of the earliest use of cyclodextrins as inverse phase transfer agents was in the Wacker oxidation of higher olefins to methyl ketones [22] with [PdCU] + [CuCU] catalyst (Scheme 10.12). Already at that time it was discovered, that cyclodextrins not only transported the olefins into the aqueous phase but imposed a substrate-selectivity, too with Ckh olefins the yields decreased dramatically and 1-tetradecene was only slightly oxidized. 

For some systems, at high concentration, inverse phases are observed. That is, one may generate an inverse hexagonal columnar phase (columns of water encapsulated by amphiphiles), or an inverse micellar phase (a bulk LC sample with spherical water cavities). 

The term Counter Phase Transfer Catalysis (CPTC) was coined by Okano214,215 to describe biphasic reactions catalysed by water soluble transition metal complexes which involve transport of an organic-soluble reactant into the aqueous phase where the catalytic reaction takes place. Similarly, Mathias and Vaidya564,565 gave the name Inverse Phase Transfer Catalysis to describe this kind of biphasic catalysis which contrasts with classical Phase Transfer Catalysis where the reaction occurs in the organic phase and does not involve formation of micelles.389,564... 

PAA can be prepared using bulk polymerization, aqueous polymerization, nonaqueous polymerization, inverse phase emulsion and suspension polymerization. The precise structure of the resulting PAA chain is dependent upon many factors including the polymerization process and conditions. The tacticity of... 

Following the thermodynamical laws, the order within the individual mesophases increase normally during cooling. In some very special cases (e.g. for polar molecules) sometimes an inverse phase sequence occurs, where cooling gives rise to a less ordered phase like a nematic phase at low temperature. This phenomenon, so-called re-entrance, has been well investigated and different models have been proposed to explain the behaviour18,19. 

Neutral cyclodextrins have been used as chiral phase-transfer catalysts for an interesting inverse phase-transfer catalysis reaction [50]. The Markovnikovhydration of the double bond by an oxymercuration-demercuration reaction has been demonstrated in the presence of cyclodextrins as chiral phase-transfer catalysts to obtain products in low to moderate enantioselectivity (Scheme 7.16). The mercuric salts are water-soluble, and remain in the aqueous phase, whereas the neutral alkenes prefer an organic phase. A neutral cyclodextrin helps to bring the alkenes into the aqueous phase in a biphasic reaction, and also provides the necessary asymmetric environment. 

Various allylic amines and protected allylic alcohols were tested using different cyclodextrins. Although only low to moderate enantioselectivity was obtained, the method demonstrated for the first time an enantioselective inverse phase-transfer catalysis hydration reaction via an oxymercuration-demercuration process. 

Mathias, L.J. and Vaidya, R.A. (1986) Inverse phase transfer catalysis. First report of a new class of interfacial reactions./. Am. Chem. Soc., 108, 1093. Fife, W.K. and Xin, Y. (1987) Inverse phase-transfer catalysis probing its mechanism with competitive transacylation. J. Am. Chem. Soc., 109, 1278. 

AhfatNM, et al. 2000. An exploration of inter-relationships between contact angle, inverse phase gas chromatography and triboelectric charging data. Eur. J. Pharm. Sci. 9 271-276. 

Riedl, B. Prud homme, R. E., "Thermodynamic Study of Poly(vinyl chloridel/Polyester Blends by Inverse-Phase Gas Chromatography at 120 C," J. Polym. Sci., Polym. Phys. Ed., 24, 2565 (1986). 

Phase Inversion Phase inversion is the process whereby a system changes from an oil-in-water emulsion to a water-in-oil emulsion, or vice versa (Figure 5). Phase inversion is an essential step in the manufacture of a number of important food products, including butter and margarine (1, 60, 85). In most other foods, phase inversion is undesirable because it has an adverse effect on the products appearance, texture, stability, and taste and should therefore be avoided. 

Figure 12.24 Phase diagrams for (a) 1-monoolein in water and (b) di-dodecyl alkyl-j8-D-glucopyranosyl-rac-glycerol in water, Hn is the inverse hexagonal phase, Gn is the inverse gyroid Ia3d, and Du is the inverse double-diamond Pn3m phase. In the inverse phases, the aqueous phase is inside the channels. [Part (a) Reprinted with permission from Larsson et al.. Journal of Physical Chemistry 93 7304 Copyright 1989, American Chemical Society. Part (b) Reprinted with permission from EDP Sciences.]...

Cubic strut phases are common in the phase diagrams of two-tailed surfactants. These surfactants have a relatively high value of the vfaolc parameter, because the volume-to-length ratio v/i(. of the double tail is twice that of a single tail. A high value of v/aoic is consistent with the formation of type II bicontinuous and other inverse phases, such as the inverse hexagonal phase in Fig. 12-24. 

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