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Perfluorinated gases

NMR Relaxation Behavior of Perfluorinated Gases 3.5.3.1 Introduction to Gas Phase Relaxation... [Pg.306]

S. D. Beyea, A. Caprihan, C. F. M. Clewett, S.J. Glass 2002, (Spatially resolved adsorption isotherms of thermally polarized perfluorinated gases in Y-TZP ceramic materials using NMR imaging), Appl. Magn. Reson. 22, 175-186. [Pg.320]

Direct Fluorination. This is a more recently developed method for the synthesis of perfluorinated compounds. In this process, fluorine gas is passed through a solution or suspension of the reactant in a nonreactive solvent such as trichlorotrifluoroethane (CFC-113). Sodium fluoride may also be present in the reaction medium to remove the coproduct hydrogen fluoride. There has been enormous interest in this area since the early 1980s resulting in numerous journal pubHcations and patents (7—9) (see Fluorine compounds, organic-direct fluorination). Direct fluorination is especially useful for the preparation of perfluoroethers. [Pg.298]

Pubhcations have described the use of HFPO to prepare acyl fluorides (53), fluoroketones (54), fluorinated heterocycles (55), as well as serving as a source of difluorocarbene for the synthesis of numerous cycHc and acycHc compounds (56). The isomerization of HFPO to hexafluoroacetone by hydrogen fluoride has been used as part of a one-pot synthesis of bisphenol AF (57). HFPO has been used as the starting material for the preparation of optically active perfluorinated acids (58). The nmr spectmm of HFPO is given in Reference 59. The molecular stmcture of HFPO has been deterrnined by gas-phase electron diffraction (13). [Pg.304]

Direct fluorination involves the treatment of an appropriate hydrocarbon precursor dissolved in an inert Hquid with fluorine gas to yield a perfluorinated precursor to a long-chain carboxyflc acid. Equations 2 and 3 illustrate the process for perfluorooctadecanoic acid (17). [Pg.310]

Fluorinated polymers, especially polytetrafluoroethylene (PTFE) and copolymers of tetrafluoroethylene (TFE) with hexafluoropropylene (HFP) and perfluorinated alkyl vinyl ethers (PFAVE) as well as other fluorine-containing polymers are well known as materials with unique inertness. However, fluorinated polymers with functional groups are of much more interest because they combine the merits of pefluorinated materials and functional polymers (the terms functional monomer/ polymer will be used in this chapter to mean monomer/polymer containing functional groups, respectively). Such materials can be used, e.g., as ion exchange membranes for chlorine-alkali and fuel cells, gas separation membranes, solid polymeric superacid catalysts and polymeric reagents for various organic reactions, and chemical sensors. Of course, fully fluorinated materials are exceptionally inert, but at the same time are the most complicated to produce. [Pg.91]

In Figure 1 are shown three negative ion APIMS spectra of perfluoromethylcy-clohexane (C7F,4) that were obtained under three different ion source conditions. It is well known that perfluorinated molecules of this size attach thermal electrons very rapidly to form molecular anions by the resonance electron capture (EC) mechanism (e + M M"), and this is what is observed in Figure la where pure nitrogen buffer gas has been used. In the use of certain analytical instruments for the detection of such compounds, however, protic molecules such as water or... [Pg.221]

Perfluorinated hydrocarbons are much weaker eluents ilthan aliphatic hydrocarbons and they can have negative e" values. They are"useful for separating nonpolar sample components such as aliphatic >ydrocarbons, olefins, and benzene. However, their limited solubility fof the higher alkanes (> C,() and their high cost limits their use as eluents, particulariy because the separation of such samples can also be porjbrmed by gas chromatography. ... [Pg.210]

The aUcoxylamines have a >N—O—C substrucmre and may be considered O-substituted hydroxylamine ethers. The simplest example of these species is MeONH2 with a gas phase enthalpy of formation of —25.1 kJmol which was discussed in a previous section. Consider now the perfluorinated species (CF3)2N0CF2CF20N(CF3)2 and its synthesis shown in equation 9. [Pg.59]

Another interesting aspect of perfluorinated liquids is their high gas solubility. They can provide highly effective gas transport in chemical reactions and physical processes. In addition, PFCs can be used to absorb or scavenge gases. Table 6.8 shows the solubility of various gases in a perfluorohexane. [Pg.118]

Substantial progress has been made to carry out alkylation in the gas phase over solid superacid catalysts. Nafion-H, a perfluorinated resin-sulfonic acid, for example, catalyzes the methylation of benzene and methylbenzenes with methyl alcohol under relatively mild conditions. The reaction shows low substrate selectivity.203... [Pg.246]

For larger saturated rings only perfluorinated derivatives have been studied in the gas phase. No data have been reported for perfluorocyclopentane, and five-membered rings containing S(II), S(IV) and S(VI) are considered instead (Table 15). Within their experimental error limits, the C—F bond distances in these perfluorinated cyclic compounds are... [Pg.43]

Pyridinium (trifluoroacetyl)methylide forms [3-1-2] cycloadducts with a wide variety of perfluorinated and partially fluorinated olefins, alkynes, and nitriles [86JFC(34)275]. Photolysis of a mixture of hexafluoro-3-diazobutan-2-one and perfluoro-2-butyne in the gas phase results in the formation of tetrakis(trifluoromethyl)furan a ketocarbene is the key intermediate of this reaction sequence (87JOC2680) (Scheme 79). [Pg.40]


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NMR Relaxation Behavior of Perfluorinated Gases

Perfluorinated

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