Hydrogen fluoride fluorinated hydrocarbons

CoF is used for the replacement of hydrogen with fluorine in halocarbons (5) for fluorination of xylylalkanes, used in vapor-phase soldering fluxes (6) formation of dibutyl decalins (7) fluorination of alkynes (8) synthesis of unsaturated or partially fluorinated compounds (9—11) and conversion of aromatic compounds to perfluorocycHc compounds (see Fluorine compounds, organic). CoF rarely causes polymerization of hydrocarbons. CoF is also used for the conversion of metal oxides to higher valency metal fluorides, eg, in the assay of uranium ore (12). It is also used in the manufacture of nitrogen fluoride, NF, from ammonia (13). 

Initial attempts at reactions between fluorine and hydrocarbons were described as similar to combustion and the reaction products contained mostly carbon tetrafluoride and hydrogen fluoride ... 

Fluorides. Tantalum pentafluoride [7783-71-3] TaF, (mp = 96.8° C, bp = 229.5° C) is used in petrochemistry as an isomerization and alkalation catalyst. In addition, the fluoride can be utilized as a fluorination catalyst for the production of fluorinated hydrocarbons. The pentafluoride is produced by the direct fluorination of tantalum metal or by reacting anhydrous hydrogen fluoride with the corresponding pentoxide or oxychloride in the presence of a suitable dehydrating agent (71). The ability of TaF to act as a fluoride ion acceptor in anhydrous HF has been used in the preparation of salts of the AsH, H S, and PH ions (72). The oxyfluorides TaOF [20263-47-2] and Ta02F [13597-27-8] do not find any industrial appHcation. 

Chlorine dioxide Copper Fluorine Hydrazine Hydrocarbons (benzene, butane, propane, gasoline, turpentine, etc) Hydrocyanic acid Hydrofluoric acid, anhydrous (hydrogen fluoride) Hydrogen peroxide Ammonia, methane, phosphine or hydrogen sulphide Acetylene, hydrogen peroxide Isolate from everything Hydrogen peroxide, nitric acid, or any other oxidant Fluorine, chlorine, bromine, chromic acid, peroxide Nitric acid, alkalis Ammonia, aqueous or anhydrous Copper, chromium, iron, most metals or their salts, any flammable liquid, combustible materials, aniline, nitromethane... 

Before fluorination, the dielectric constant ofpoly(bisbenzocyclobutene) was 2.8, and this value was reduced to 2.1 after plasma treatment. No data were reported in the paper on characterization of structure or properties, except for the dielectric constant of the modified poly(bisbenzocyclobutene). The authors did report that the thermal stability offluorinatedpoly(vinylidenefluoride) was inferior to the original poly(vinylidenefluoride) when treated in a similar way. One of the probable reasons for the low thermal stability is that the NF3 plasma degraded the polymer. According to their results, the thickness of fluorinated poly(bisbenzo-cyclobutene) was reduced by 30%. The same phenomenon was observed for other hydrocarbon polymers subjected to the NF3 plasma process. A remaining question is whether plasma treatment can modify more than a thin surface layer of the cured polymer Additionally, one of the side products generated was hydrogen fluoride, which is a serious drawback to this approach. 

Electrochemical fluorination in anhydrous hydrogen fluoride (Simons process) involves electrolysis of organic compounds (ahphatic hydrocarbons, haloalkanes, acid halides, esters, ethers, amines) at nickel electrodes. It leads mostly to perfluori-nated compounds, but is accompanied to a high extent by cleavage and rearrangement reactions. The mechanism of the formation of carbocations according to Eq. (1) and Scheme 1 is assumed... 

Table 20.1 onic Fluorination of Tertiary Hydrocarbons with NO + BF4/ Pyridine Poly(hydrogen fluoride) (PPHF)88... 

Since the time of the earliest work concerned with the reaction of hydrocarbons and fluorine in 1890 by Moissan (who isolated fluorine in 1886), numerous difficulties have been reported. According to Lovelace et al the action of fluorine on a carbon compound can be likened to a combustion process where the products are carbon tetrafluoride and hydrogen fluoride (1). 

Disproportionation of halogenatcd aliphatic hydrocarbons can also be accomplished using catalysts based on chromium oxides with the formula Cr01 2F2 1.18 This catalytic material is obtained by fluorination w ith hydrogen fluoride of an oxide hydrate of trivalent chromium with the formula Cr203 xH,0 (with x = 1-9). The chromium oxide hydrate is reacted with a mixture of hydrogen fluoride/nitrogen gas in a molar ratio of 1 10 in an externally heated nickel tubular reactor at 350 450 C. 

Additions of halogen fluorides to the more electrophilic peifluonnated olefins generally require different conditions Reactions of iodine fluoride, generated in situ from iodine and iodine pentafluonde [62 102 103, 705] or iodine, hydrogen fluoride, and parapenodic acid [104], with fluorinated olefins (equations 8-10) are especially well studied because the perfluoroalkyl iodide products are useful precursors of surfactants and other fluorochemicals Somewhat higher temperatures are required compared with reactions with hydrocarbon olefins Additions of bromine fluoride, from bromine and bromine trifluonde, to perfluormated olefins are also known [106]... 

Hydrogen Fluoride-Trifluoromethanesulfonic Acid. The acidity of this binary Brpnsted acid system has not been measured, but the superacidic properties are mentioned in numerous patents concerning fluorination, olefin alkylation, and hydrocarbon conversion. 

The addition of hydrogen fluoride to halogenated alkenes is no less important than the addition to olefinic hydrocarbons. The replacement of chlorine by fluorine often accompanies the hy-drofluorination of halogenated alkenes. ... 

Either fusion with alkali metals or reaction with aUcali-metal complexes with aromatic hydrocarbons will break down most fluorocarbon systems, due to the high electron affinities of these systems. Such reactions form the basis of some methods of elemental analysis [13], the fluorine being estimated as hydrogen fluoride after ion exchange. Surface defluorination of PTFE occurs with alkali metals and using other techniques [14]. Per-fluorocycloalkanes give aromatic compounds by passage over hot iron and this provides a potential route to a variety of perfluoroaromatic systems (Chapter 9, Section IB). 

HYDRoaEN fluoride rarely occurs free in nature but its presence has been detected in the effluvia from vents in volcanic districts for example, R. V. Matteucci found it in the gaseous products of the fumeroles of Vesuvius. Hydrogen fluoride is formed by the direct union of the elements and by the action of fluorine on water, ammonia, hydrocarbons, and many organic compounds. It is also formed by the action of steam on some of the metal fluorides—-lead fluoride, silver fluoride, etc.—and by the action of some fluorides on water—e.g. iodine pentafluoride. The fluorides and fluosilicates are decomposed by sulphuric acid, with the evolution of hydrogen fluoride—the reaction is incomplete with hydrochloric acid in place of sulphuric acid. G. Gore used chromic fluoride and sulphuric acid R. Luboldt decomposed cryolite with the same acid. 

A different stereochemical behavior has, however, been observed in methanol . In this solvent XeF, reacts with the solvent to form an unstable reactive species (CHsOXeF), which gives quantitatively formaldehyde by disproportionation in the absence of unsaturated hydrocarbons or with unreactive alkenes. Hydrogen fluoride generated in situ complexes the electrophilic CHsOXeF species to form a protonated derivative a which reacts with activated dienes such as 2,3-dimethylbutadiene, as an apparent fluorine electrophile to give 1,4- and 1,2-fluoromethoxy products, together with 1,2- and 1,4-difluoro derivatives (equation 25). 

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