Reaction with fluoroalkane

This explains the low probability that thermal fluorocarbon car-bonlum ions undergo F transfer reactions with fluoroalkanes (Table I). 

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)... 

The equilibrium position of the reaction depends on the nucleophilicity of the anion, whether a good leaving group is present, and whether one anion is better stabilized than the other in a given solvent. For example, reactions with KF will thus lead cleanly to fluoroalkanes, because fluoride is such a poor leaving group due to the stability of the C-F bond. 

Fluoroalkanes have also been prepared from the vapour phase reactions of fluoroalcohols, CFjCCF lnCHjOH (n = 0, 1 or 2), with phosgene and HF over an HF-activated 7-alumina catalyst, at temperatures above 250 C. The products of these reactions are CFj(CF j) CHjF, and are potential CFC replacements [1481b]. The related compounds CHF j(CF j) CHjF (n = 1 or 3) have also been prepared under similar conditions from CHF j(CF j) CH jOH. However, when the fluoroalcohol contains more than one methylene unit between the OH and CF groups, reaction with COClj and HF results in dehydration to the alkene [1481b] e.g. 

In Table I, we also estimate the probabilities that the collisions between these reactant pairs lead to reaction. Except for the reactions of CF2, we see that the F or F transfer reactions observed in perfluorinated alkanes are extremely inefficient. This low reaction probability is especially striking when compared with the efficiencies of the corresponding reactions in hydrocarbon systems ( ). The methyl ion reaction with ethane corresponding to reaction 4 occurs at every collision between the reactant pair the hydride transfer reactions from propane to vinyl ions or ethyl ions, corresponding to reactions 6 and 7, occur with efficiencies of about 0.5. These differences between the efficiencies of ion-molecule reactions in fluoroalkanes and alkanes can be explained in terms of the thermochemistry of these systems, remembering that endothermic or thermoneutral ion-molecule reactions are quite inefficient, and often can not even be seen on the time scale of ion collection in a mass spectrometer. The highly efficient hydride transfer reactions observed in hydrocarbon systems are all exothermic. In the fluorocarbon systems, o the other j hand, the F transfer reactions listed for 2 3 2 5 actually slightly endothermic, as... 

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... 

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

The mixtures bromine trifluoride/bromine and iodine pentafluoride/iodine can be successfully employed to prepare bromo- and iodo-substituted fluoroalkanes by addition to poly-fluoroalkenes. The reactions are carried out, in the presence of catalysts aluminum, aluminum/ aluminum triiodide9 or without a catalyst,10 in steel reactors at room temperature or with heating. In most cases the addition products are obtained in high yield (see Table 1). 

The result of the reaction of sulfur tetrafluoride with alcohols strongly depends on the structure of the alcohol. Simple aliphatic alcohols, such as methanol, ethanol and propan-2-ol, give alkyl ethers as the main product with only small amounts of fluoroalkanes.41 42 Yields of fluorinated products increase with increasing acidity of the hydroxy group and, in general, the reaction is only synthetically useful with alcohols equally or more acidic than tropolone (p K, = 6.42). 

The type of products formed in reactions of /(-hydroxy acids with sulfur tetrafluoride depends on the substituents on the carbon alom adjacent to the hydroxy group. Acids such as 3-hy-droxypropanoic acid (21) and 3-hydroxybutanoic acid (22) give, in addition to 1,1,1,3-tetra-fluoroalkanes, mainly dimeric products, i.e. fluorinated esters or ethers, together with small amounts of unsaturated acid fluorides. In contrast, n7C -4,4,4-trifluoro-3-hydroxybutanoic acid (23), depending on the reaction conditions, affords 3,3,3-trifluoro-l-(lrifluoromethyl)propyl fluorosulfite or a mixture of 1,1,1.2,4,4,4-hcptafluorobutanc and l,l,1.4.4,4-hcxafluorobut-2-ene.116... 

Hydroxy-1,2-dicarboxylic acids, such as n- and L-a-hydroxysuccinic acid53 and D-tartaric acid.120 on treatment with sulfur tetrafluoride give complex mixtures of fluoroalkanes, fluoro-alkenes, fluoroalkyl fluorosulfites and cyclic five-membered ethers, derivatives of 2.2,5.5-tet-rafluorotetrahydrofuran. In the case of D-tartaric acid the cyclic ethers are predominant components (64%) of the reaction mixture.120 Linear and cyclic mono- and disulfites formed in these reactions give, after hydrolysis, the corresponding linear and cyclic polyfluoro alcohols and diols in high yield.53120... 

Reaction of AT-fluorobis(trifluoromethylsulfonyl)amine (Id) with alkenes gives various products, depending on the reaction conditions and the structure of the substrate. In solvents of higher nucleophilicity such as water, acetic acid, aqueous hydrochloric acid, and 70 % hydrogen fluoride/pyridine, a-fluorohydrins or their acetates, a-chloro-fl-fluoroalkanes or a,/ -difluoroal-kanes, e.g. 14. are obtained.146 Reaction of styrene and ( >l-phenylpropene with Id in dich-loromethane/acetic acid gives l-acetoxy-2-fluoro-l-phenylethane and -propane, in 92 and 99 % yield, respectively, the latter product in a ratio (erythrojthreo) 1 l.146... 

Fluoroalkyl iodides are oxidized at the iodine atom by trifluoroperacetic acid3 7- 19 or by a mixture of trifluoroacetic anhydride with hydrogen peroxide the products are [bis(trifluoro-acetoxy)iodo]fluoroalkanes, e.g. oxidation of 1 to 2. The iodine atom oxidized in the reactions can be attached either to a nonfluorinated317 318 or a fluorinated carbon atom.319... 

Reaction of perfluoropropene with diethylamine yields (F)-fluoroenaminc 3 and fluoro-alkylamine 4 in a 1 1 or 3 1 mixture (depending on the reaction conditions used). This mixture is known as Ishikawa s reagent and can be used (without separation) for the transformation of alkyl alcohols to fluoroalkanes (see Vol. ElOb/Part 1. p99).218... 

The labeling of complex compounds can also be achieved by attaching small units, already containing the positron-emitting fluorine isotope, to the main molecular skeleton. Bifunctional fluoroalkanes 18F(CH2) X (n = 1-3, X =Br, OMs, OTs) could be prepared in > 90% radiochemical yield within 10 min. These compounds, especially the tosylates, were then reacted with phenols to give the corresponding [18F]fluoroethers390. Such a reaction... 

The reaction of fluorine or xenon difluoride with iodoaUcanes gives fluoroalkanes by similar processes [53, 54]. 

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