Fluoroalkanes

Cosolvents ana Surfactants Many nonvolatile polar substances cannot be dissolved at moderate temperatures in nonpolar fluids such as CO9. Cosolvents (also called entrainers, modifiers, moderators) such as alcohols and acetone have been added to fluids to raise the solvent strength. The addition of only 2 mol % of the complexing agent tri-/i-butyl phosphate (TBP) to CO9 increases the solubility ofnydro-quinone by a factor of 250 due to Lewis acid-base interactions. Veiy recently, surfac tants have been used to form reverse micelles, microemulsions, and polymeric latexes in SCFs including CO9. These organized molecular assemblies can dissolve hydrophilic solutes and ionic species such as amino acids and even proteins. Examples of surfactant tails which interact favorably with CO9 include fluoroethers, fluoroacrylates, fluoroalkanes, propylene oxides, and siloxanes. 

Carboxylic acids react with xenon difluoride to produce unstable xenon esters The esters decarboxylate to produce free radical intermediates, which undergo fluonnation or reaction with the solvent system Thus aliphatic acids decarboxylate to produce mainly fluoroalkanes or products from abstraction of hydrogen from the solvent Perfluoro acids decarboxylate in the presence of aromatic substrates to give perfluoroalkyl aromatics Aromatic and vinylic acids do not decarboxylate [91] (equation 51)... 

Simple a-fluorosulfides are reduced to the fluoroalkanes by sodium-ethanol [9J (equation 75). Clean conversion of bis(trifluoromethyl) diiulfide to trifluoromethyl mercaptan is accomplished with hydrogen sulfide and ultraviolet irradiation (941 (equation 76). Perfluoroalkanesulfonyl fluondes are converted to the sulfmate salts by hydrazine [95] (equauon 77)... 

Electrolysis of carboxylic acid salts m solution causes decaboxyladve coupling similar to Kolbe reaction. Thus, eleclrolysis of 3,3,3-trifluoro-2-trifluoromethyl-propanoic acid in die presence of some of its potassium salt gives the corresponding fluoroalkane in a satisfactory yield [7d] (equation 67). 

Many reactions of fluorinated organics with metal halides result in the replacement of fluorine with halogen A general route to 1,1,1-trichloro- or tribromo-fluoroalkanes involves treating primary fluoroalkyl iodides with aluminum trichloride or aluminum tribromide [74], Benzylic [75, 76] or vinylic [72] fluorine can be exchanged for chlorine when treated with aluminum trichloride... 

The high thermal and chemical stability of fluorocarbons, combined with their very weak intermolecular interactions, makes them ideal stationary phases for the separation of a wide variety of organic compounds, including both hydrocarbons and fluorine-containing molecules Fluonnated stationary phases include per-fluoroalkanes, fluorocarbon surfactants, poly(chlorotrifluoroethylene), polyfper-fluoroalkyl) ethers, and other functionalized perfluoro compounds The applications of fluonnated compounds as stationary phases in gas-liquid chroma... 

Figure 3.7 provides a typical 13C NMR spectrum of a secondary fluoroalkane, that of 2-fluoropentane. In it, one can detect coupling to the fluorine substituent at all carbons except C-5. 

H and13C NMR Data for Halofluoroalkanes. Scheme 3.13 provides some pertinent proton and carbon chemical shift and coupling constant data for fluorochloro- and fluorobromomethanes, whereas Scheme 3.14 contains relevant data for some typical halo fluoroalkanes. There does not appear to be anything unusual going on here. 

A nucleophile is a species that attacks electron-deficient sites and donates a lone pair of electrons to form a covalent bond. Halogenoalkanes get more reactive as the C-X bond gets longer and therefore weaker. Iodoalkanes therefore react fastest and fluoroalkanes slowest. 

Fluoroalkanes have been prepared by the catalytic reaction of fluoride ion with diazoalkanes, but little synthetic use has been made of the process [38],... 

Starting material Reaction conditions % yield of fluoroalkane... 

Alkyl fluorides are for practical purposes resistant to reduction. In a few instances, where fluorine in fluoroalkanes was replaced by hydrogen, very energetic conditions were required and usually gave poor yields 500, SOI], For this reason it is not difficult to replace other halogens present in the molecule without affecting fluorine. 

G.G. Belen kii, V.A. Petrov, P.R. Resnick, Electrophilic, catalytic alkylation of poly-fluoroolefins by some fluoroalkanes, J. Fluorine Chem. 108 (2001) 15-20. 

A. Saito, M. Nakagawa, T. Taguchi, Chromium-mediated fluoroalkenylation reactions of 1,1-dibromo-1-fluoroalkane and 1-bromo-1-fluoroalkene derivatives, J. Fluor. Chem. 126 (2005) 1166-1173. 

A further technique said to be useful on an industrial scale for the ECF conversion of alkanesulphonyl fluoride and tetramethyl sulphone to form per-fluoroalkane sulphonyl fluorides involves the continuous extraction of products from the electrolyte and hydrogen gas stream. The method claims high yields (93%) without recovery problems of prior art [151]. 

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