Fluorination of hydrocarbons

This reaction has often reached explosive proportions in the laboratory. Several methods were devised for controlling it between 1940 and 1965. For fluorination of hydrocarbons of low (1—6 carbon atoms) molecular weight at room temperature or below by these methods, yields as high as 80% of perfluorinated products were reported together with partially fluorinated species (9—11). However, fluorination reactions in that eta involving elemental fluorine with complex hydrocarbons at elevated temperatures led to appreciable cleavage of the carbon—carbon bonds and the yields invariably were only a few percent. 

Carbonyl sulfonyl fluorides of the formula FC0(CF2) S02F have been prepared by electrochemical fluorination of hydrocarbon sultones (41,42). More commonly in a technology pioneered by Du Pont, perfluoroalkanecarbonyl sulfonyl fluorides are prepared by addition of SO to tetrafluoroethylene followed by isomerization with a tertiary amine such as triethylamine (43). 

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. 

Of great practical value is the thorough fluorination of hydrocarbons and other organic compounds, which can be used to produce valuable perfluorinated substances for example,... 

Peduoropolyethers, which constitute special class of fluoropolymer, are useful as lubricants,1 elastomers,2 and heat-transfer fluids under demanding conditions. Several commerical products are available, which are generally prepared by ring-opening polymerization of hexafluoropropylene oxide or by the random copolymerization oftetrafluoroethylene and hexafluoropropylene with oxygen under ultraviolet irradiation.3 Direct fluorination of hydrocarbon ethers has been reported4 but must be done very slowly under carefully controlled... 

We discovered another synthetic technique that involves the conversion by direct fluorination of hydrocarbon polyesters to perfluoropolyesters followed by treatment with sulfur tetrafluoride to produce new perfluoropolyethers.42 The first paper in this area ofreasearch reported that conversion of poly(2,2-dimethyl-1,3-propylene succinate) and poly( 1,4-butylene adipate) by using the direct fluorination to produce novel branched and linear perfluoropolyethers, respectively. The structures are shown in Figure 14.6. The second paper concerns the application of the direct fluorination technology base directed toward oligomers, diacids, diesters, and surfactants.43... 

The effect of successive fluorination of hydrocarbons on bond lengths has been extensively discussed in a recent review article which summarizes the most important experimental trends316). These trends are nicely accounted for by the LCFC approach. 

Cobalt(III) fluoride is used as a fluorinating agent for fluorination of hydrocarbons (Fowler process). 

Like perfluorinated polymers, perfluorinated fluids are both chemically and thermally very stable. Originally developed during the Manhattan Project their commercial application dates from the 1960s. There are two major production methods, cobalt(III) fluoride fluorination of hydrocarbons and electrochemical fluorination. The first route involves the fluorination of a stirred or fluidized bed of cobalt(II) fluoride to cobalt(III) fluoride with elemental fluorine at... 

Examples of accomplishments in this field include the fluorination of hydrocarbon phosphanes and diphosphancs to yield perfluorinated 25-phosphanes (Table 5).22,23... 

Fluorination of Alkanes. Fluorination of alkanes is extremely difficult to control. The reaction usually results in substantial C—C bond rupture and can readily lead to explosion.136 However, several methods for controlled direct radical fluorination of hydrocarbons have been developed. The key and obvious observation was that the only reaction sufficiently exothermic to cause fragmentation is the termination step between a carbon radical and a fluorine atom. Consequently, if the atomic fluorine population and the mobility of hydrocarbon radicals are minimized, controlled fluorination becomes feasible. 

Fluorination of hydrocarbons can only be performed electrochemically in HF solution at nickel electrodes. A typical example for this technically extremely important process is [14] ... 

Cobalt trifluoride is used almost exclusively to replace hydrogen on carbon and in oxidative fluorination of hydrocarbons, for example, equations (13) and (14). Zinc fluoride, Sbp3, and Pbp2 are mild fluorinating reagents that can often be used to give partially fluorinated... 

Caesium fluoroxysulphate (CSSO4F) [94] is a solid electrophilic fluorinating agent that is very easily prepared [100] (Figure 3.14) but, unfortunately, is very prone to rapid uncontrolled decomposition. However, it has been used for the fluorination of hydrocarbons [101] and aromatics [102-104] (Figure 3.15). 

Fluorination of hydrocarbons, such as adamantane, is possible using a mixture of nitrosonium tetrafluoroborate and pyridine HF [143] (Figure 3.18). 

USE In the fluorination of hydrocarbons. Caution Symptoms due to fluoride. Highly toxic. 

Cobalt fluoride (C0F3) Cobalt trifluoride Cobaitic fluoride EINECS 233-062-4. Used as a fluorinating agent in the fluorination of hydrocarbons (Fowler process). Solid d = 3.88 reacts with air and H2O. Atomergic Chemetals Cerac, ElfAtochem N. Am. 

Gas-phase fluorination of hydrocarbon heterocycles using C0F3 as fluorinating agent was successfully apphed for the preparation of some perfluorinated heterocychc compounds" (see Fig. 9.9). 

Phthalides have an extremely high oxidative potential (2.86 V) (03GC512). Selective fluorination also takes place in the case of carbonyl-containing heterocyclic compounds. Thus mono- and difluoro derivatives of 4-(metho-xyphenyl)acetone and ethyl 4-(methoxyphenyl)acetate (87TL2359, 98JFC(87)215) and fluoroindanes (90TL3137) are produced by anodic fluorination of hydrocarbon substrates in the... 

Full details have been published of the direct fluorination of hydrocarbon polymers by the so-called LaMar procedure, - the principal feature of which is infinite dilution initially with helium or nitrogen followed by gradient changes of fluorine concentration with substrate particie sizes greater than 100 mesh a hydrocarbon core is retained, and large fabricated items such as polyethylene bottles can... 

Even electrophilic fluorination of alkanes has been reported. F2 and fluoroxytrifluoro-methane have been used to fluorinate tertiary centers in steroids and adamantanes by Barton and coworkers ". The electrophilic nature of a reaction involving polarized but not cationic fluorine species has been invoked. Gal and Rozen have carried out direct electrophilic fluorination of hydrocarbons in the presence of chloroform. F2 appears to be strongly polarized in chloroform (hydrogen bonding with the acidic proton of CHCI3). However, so far no positively charged fluorine species (fluoronium ion) is known in solution chemistry. 

Uses Fluorination of hydrocarbons Manuf./Distrib. Aldrich http //www.sigma-aidrich.com] Atofina... 

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