Anionic perfluoropolyether ammonium

Similar transformations were used to demonstrate the possibility of using water/ CO2 microemulsions as reaction media, which were stabilized using the anionic perfluoropolyether ammonium carboxylate surfactant [PFPECOO] [NH4] [25]. No additional phase transfer catalysts are necessary under these conditions. For example, the reaction between potassium bromide and benzyl chloride to form benzyl bromide [Eqs. (2)-(4)] resulted in a much better yield in the H2O/CO2 system than in a conventional water-in-oil microemulsion. 

An interesting new type of reaction system is that of water-in-carbon dioxide microemulsions. Several nucleophilic substitution reactions have been performed in such a system using an anionic perfluoropolyether ammonium carboxylate surfactant. The reactions studied were considerably fas-... 

The use of sc C02 instead of toluene as a solvent leads to some rate enhancement in these two systems, although it is clear that this activity is still not practical for most nonpolar, nonvolatile substrates. Significant improvements to the biphasic water/supercritical C02 system were accomplished by forming H20/C02 emulsions using newly developed surfactants (Jacobson et al., 1999). Three different surfactants were used that form water in C02 (w/c) or C02 in water (c/w) emulsions (1) anionic surfactant perfluoropolyether ammonium carboxylate, (2) cationic Lodyne 106A, and (3) nonionic poly(butylene oxide)-h-poly(ethylene oxide). The low interfacial tension, y, between water and C02 (17 mNm-1 at pressures above 70 bar), which is significantly lower than water/alkane systems (30-60 mNm-1),... 

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