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Fluorinated crown ethers

In related work,20 these same authors evaluated a fluorinated crown ether carboxylic acid,. rym-difluorobenzo-16-cniwn-5 oxyacetic acid, for use in the SCF extraction of uranyl ion and lanthanides, again from a cellulose matrix. Although this compound... [Pg.619]

Figure 2.40 Euminescent fluorinated crown-ether-isocyanide gold(I) metallo-mesogens... Figure 2.40 Euminescent fluorinated crown-ether-isocyanide gold(I) metallo-mesogens...
Simple and Complex Organic Molecules. Using modem direct fluorination technology, the synthesis of even the most complex perfluorocarbon stmctures from hydrocarbon precursors is now possible. For example, syntheses of the first perfluoro crown ethers, perfluoro 18-crown-6, perfluoro 15-crown-5, and perfluoro 12-crown-4 (54) have been reported. Perfluoro crown ethers (54,55) are becoming important as the molecules of choice for many F-nmr imaging appHcations (56) in humans and are particularly effective in brain and spinal diagnostics when... [Pg.278]

Grown Ethers. Ethylene oxide forms cycHc oligomers (crown ethers) in the presence of fluorinated Lewis acids such as boron tritiuoride, phosphoms pentafluoride, or antimony pentafluoride. Hydrogen fluoride is the preferred catalyst (47). The presence of BF , PF , or SbF salts of alkah, alkaline earth, or transition metals directs the oligomerization to the cycHc tetramer, 1,4,7,10-tetraoxacyclododecane [294-93-9] (12-crown-4), pentamer, 1,4,7,10,13-pentaoxacyclopentadecane [33100-27-6] (15-crown-6), andhexamer, 1,4,7,10,13,16-hexaoxacyclooctadecane [17455-13-9]... [Pg.453]

Saturated hydrocarbons such as neopentane, notbomane, and cyclooctane have been converted to the corresponding perfluoro derivatives in 10-20% yield by gas-phase reaction with fluorine gas diluted with helium at —78°C. Simple ethers can be completely fluorinated under similar conditions. Crown polyethers can be fluorinated by passing an Fa/He stream over a solid mixture of sodium fluoride and the crown ether. Liquid-phase fluorination of hydrocarbons has also been observed, but the reaction is believed to be ionic, rather than radical, in character. A variety of milder fluorination agents have been developed for synthetic purposes and will be discussed in Chapter 6 of Part B. [Pg.705]

Under carefully controlled conditions even complex molecules can be fluorinated. For example, the preparation of perfluoro-crown ethers (85CC1350) and perfluoro(2.2.2.)-cryptand (90JOC5933) has been described. Branched morpholines and piperazines have been directly fluorinated to their perfluoro analogues [90JFC(50)15],... [Pg.3]

Triorganotin fluorides can be prepared by the use of new fluorinating systems. 18-Crown-6 or dibenzo-24-crown-8 can act as solid-liquid phase transfer catalysts for CsF. Trialkyltin mercaptides can be fluorodestannylated by CsF in the presence of crown ethers or alkyl bromides358 ... [Pg.523]

The small effect on reaction rates of the addition of crown ethers to the lower alcohols was also observed in the reaction of potassium acetate with 1-bromobutane in ethanol (Hirao et al., 1978a,b). The displacement of fluorine in either o-nitro- or p-nitro-fluorobenzene by a methoxy group, by reaction with potassium methoxide in methanol was hardly influenced by the presence of dicyclohexyl-18-crown-6 (Del Cima et al., 1973). Mariani et al. (1978), too,... [Pg.315]

T. Irie, K. Fukushi, T. Ido, T. Nozaki, Y. Kasida, F-18-labeled fluorination by crown ether metal fluoride. 1. On labeling F-18-21-fluoroprogesterone, Int. J. Appl. Radiat. Isot. 33 (1982) 1449-1452. [Pg.57]

Fluorinations by alkali metal fluorides are often carried out in high-boiling solvents. Crown ethers have been used to solvate inorganic fluorides by complexation. [Pg.87]

Introduction of Fluorine with Alkali Metal Fluorides, Including Ammonium Fluoride and Tetraalkylammonium Fluorides (Including Special Methods of Fluorinations, e. g., Phase Transfer Catalysis, Activation by Crown Ethers, Reagents... [Pg.548]

The chlorine —fluorine exchange in l-chloro-2,4-dinitrobenzene has been systematically investigated using potassium fluoride among other reagents in the presence of several crown ethers.93... [Pg.566]

Fig. 12 Selected examples of taper shaped crown ethers and polyethers with three fluorinated chains (77°C) data refer to compounds 30, 32 and 34 [132-135]... Fig. 12 Selected examples of taper shaped crown ethers and polyethers with three fluorinated chains (77°C) data refer to compounds 30, 32 and 34 [132-135]...
Delmau et al. (129) studied the self-association of fluorinated alcohols used as diluent modifiers for the selective extraction of cesium from caustic media by calixarene-crown ethers. They found that the salt distribution ratio is enhanced by the modifiers and explained this by a solubilization effect of the modifier due to its amphiphilic properties. [Pg.412]

The chemistry of crown ethers and cryptands has progressed a long way from then-status as chemical curiosities. Recently Metcalfe et al.U4) have outlined the development of a fluorinated cryptand as an agent for measuring intracellular [Na+]. [Pg.125]

There were not many new developments in the use of crown ethers for fluorination during the last decade, since the basicity of the fluoride anion is also enhanced along with the nucleophilicity. What is more, cheaper substitutes such as open-chain polyethers frequently led to similar results. However, there are still some reactions which are difficult to accomplish without these complexing agents and the synthesis of /-butyl fluoroformates... [Pg.639]

The polyether carboxylate and sulfonate adducts lose crown ether on attempted sublimation. The fluorinated carboxylates and sulfonates form MF2 when thermally decomposed in dry air, whereas the nonfluorinated carboxylates form MC03.136,267 Their dissociation on sublimation makes them unattractive for scaleable CVD applications, but they show promise in MTi03 film formation by solution methods. This is discussed further in the CVD section. [Pg.309]


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See also in sourсe #XX -- [ Pg.969 ]




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Ethers fluorinated

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