Fluorinated organic liquid phases

The use of fluorinated hydrocarbons in various applications, including biomedical ones (e.g., blood substitutes), has inspired the need to study in detail interfacial phenomena at the interfaces between fluorinated organic liquid phases and aqueous surfactant solutions. It has been established that... 

The fluorous silica concept involves the selective partitioning of a fluorous-modified catalyst between an organic liquid phase and the fluorinated surface phase. In the absence of CO2, the fluorinated catalyst prefers the fluorous surface phase and remains partitioned onto the silica. When CO2 pressure is added, the catalyst will partition off of the silica and into the GXL phase (containing reactants), where homogeneous reaction can take place. After the reaction is completed, the CO2 is removed and the catalyst will partition back onto the fluorous silica surface, which can be easily recovered by filtration. A cartoon schematic is shown as Figure 2. 

Table 1 shows the kinetic data available for the (TMSjsSiH, which was chosen because the majority of radical reactions using silanes in organic synthesis deal with this particular silane (see Sections III and IV). Furthermore, the monohydride terminal surface of H-Si(lll) resembles (TMSjsSiH and shows similar reactivity for the organic modification of silicon surfaces (see Section V). Rate constants for the reaction of primary, secondary, and tertiary alkyl radicals with (TMSIsSiH are very similar in the range of temperatures that are useful for chemical transformations in the liquid phase. This is due to compensation of entropic and enthalpic effects through this series of alkyl radicals. Phenyl and fluorinated alkyl radicals show rate constants two to three orders of magnitude... 

Only a few years after the development of the homogeneous chiral Mn(salen) complexes by Jacobsen and Katsuki, several research groups began to study different immobiUzation methods in both liquid and soUd phases. Fluorinated organic solvents were the first type of Uquid supports studied for this purpose. The main problem in the appUcation of this methodology is the low solubility of the catalytic complex in the fluorous phase. Several papers were pubUshed by Pozzi and coworkers, who prepared a variety of salen ligands with perfluorinated chains in positions 3 and 5 of the saUcyUdene moiety (Fig. 2). 

The principal laws for the fluorination of polymeric hydrocarbons are the same as those described above for the simple case. Direct fluorination has been used extensively in organic chemistry (but only since the early 1970s) in low-temperature methods, where the fluorine is strongly diluted with some inert gas (helium, argon, nitrogen, krypton). One can note the La Mar, aerosol-based, and liquid-phase fluorination methods. 

H2 and then CO2 pressure were applied, forming a GXL. The fluorinated catalyst then partitioned off of the fluorinated silica support and into the CO2-expanded organic phase. The reaction was assumed to occur in the expanded liquid phase in which reactants (styrene, hydrogen) and catalyst (fluorinated Wilkinson s catalyst) are homogeneously present. After the reaction was completed, the pressure was released and the catalyst then partitioned back onto the silica surface. 

Alkanes do not usually react with xenon difluoride at room temperature, while thermally initiated fluorinations of organic molecules have received much less attention than liquid-phase reactions. Zajc and Zupan16 have shown that several hydrocarbons react with xenon difluoride when heated to 95-120 °C. Reproducible results can be observed only when a teflon jacket is used in the stainless reactor with appropriate preconditioning. Cyclohexane is converted to fluorocyclohexane, while the reaction with -hexane gives three monofluoro-substituted products. Fluorination of adamantane results in the formation of four products, from whose distribution it is evident that the difference in the reactivity between the secondary and the tertiary carbon atom is much larger than the difference between the reactivities of the primary and secondary carbon atoms of hexane. Liquid-phase functionalization of a tertiary carbon atom is observed in reactions in carbon disulfide, where 1-fluoroadamantane is formed17. 

Gas chromatographic studies of ethers, ketones, alcohols, esters, olefins, and alkanes, using columns with liquid phases containing P-diketonate complexes in squalane, revealed that the more nucleophilic organic substrates reacted more strongly with the P-diketonates than the less basic ones. Er complexes of fluorinated P-diketones (especially 3-trifluoroacetyl-d-camphor-ate, facam) reacted more strongly with these nucleophiles than did similar non-fluorinated Er complexes. The retention time of THE increased exponentially with the inverse of metal ionic radius in the facam chelates of a variety... 

Fluorinated organic solvent Organic liquid Temperature dependence of the miscibility of fluorinated phase with organic solvents Solvent and ligand costs Product contamination... 

Reasonably fast setting and strength development may be achieved if diluted phosphoric acid or solutions of some organic acids are used as the mixing liquid, instead of plain water. An addition of fluorine ions to the liquid phase also has an accelerating effect. Ammonium and alkali phosphates exhibit a catalytic effect on the reaction. 

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