Perfluorination with elemental fluorine

Perfluorinated organic bromides can be oxidatively fluonnated with elemental fluorine to derivatives containing tn- [124] and pentavalent [/25 126 127] bromine in yields up to 42% Perfluoroheptylbromine tetrafluoride has been used to fluonnate double bonds in halogenated alkenes [127]... 

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... 

The most important use of XV is its telomerization with fluoride ion to give a linear hydrofluoroacyl fluoride (XVI), that is fluorinated with elemental fluorine to give a linear perfluorinated polyether (XVIII), which is sold by Daikin as Demnum (Eq 13.18). Note that Demnum and Krytox are isomeric materials. In general, their properties are quite similar, but there are subtle differences in physical properties and in chemical stability in tribological applications. 

Preparation of the corresponding perfluoropolyethers requires a subsequent fluorination step to saturate double bonds and replace hydrogens in the "spacer" groups with fluorine. We have found that the partially fluorinated vinyl ethers produced in the polycondensation reaction undergo reaction with elemental fluorine to give the desired perfluorinated polyethers. Ultraviolet irradiation is required to replace the least reactive hydrogensl ]. 

A single-chaimel (500 pm x 500 pm x 70 mm) microreactor has been designed for use with elemental fluorine, both for selective fluorination and for perfluorination of organic compounds [61]. The addition of fluorine to the trifluorosulfur group leads to the pentafluoro derivative in 44% yield (Scheme 9.12). From the data indicating that... 

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. 

Chemical Properties. A combination of excellent chemical and mechanical properties at elevated temperatures result in high performance service in the chemical processing industry. Teflon PEA resins have been exposed to a variety of organic and inorganic compounds commonly encountered in chemical service (26). They are not attacked by inorganic acids, bases, halogens, metal salt solutions, organic acids, and anhydrides. Aromatic and ahphatic hydrocarbons, alcohols, aldehydes, ketones, ethers, amines, esters, chlorinated compounds, and other polymer solvents have Httle effect. However, like other perfluorinated polymers,they react with alkah metals and elemental fluorine. 

Oxidative addition of elemental fluorine to appropriate 1,3-dicarbonyl compounds provides a convenient synthesis of perfluorinated 1,2-dioxolanes. In this way (20) may be formed from difluoromalonyl fluoride, F2C(COF)2 <92JST(274)163>, and (39) is similarly prepared from either hexafluoroacetylacetone or the copper(II) or nickel(II) chelate of trifluoroacetylacetone with concomitant replacement of all remaining hydrogen atoms by fluorine <65JOCI429>. 

Sulfur tetrafluoride and F2 gas are among other fluorinating agents used for the synthesis of fluorinated ethers. For example, F-oxane was reported to form in the reaction of anhydride of F-glutaric acid or F-glutaryl fluoride with excess of SF4. Perfluorinated spiro-ethers 19 were prepared in high yield by exhaustive fluorination of the parent hydrocarbons using elemental fluorine. 

In order to minimize the degradation of macromolecules, the choice of solvent is not a trivial matter. Hydrogen-containing solvents are obviously not suitable, but even halogenated ones such as CFC13 or CC12FCF2C1, usually stable to fluorine, can react violently with this element when irradiated at temperatures near 0°C. We chose two perfluorinated solvents that have been proven safe and suitable for radical fluorination perfluoro-2-(butyl)-tetrahydro-duran (FC-75 Fluorinert from 3M) and hexafluoropropylene oxide (HFPO) oligomers known as Krytox +... 

The solubilities of fluorinated surfactants are related to the unusual properties of the fluorine atom and the C—F bond. Fluorine is the most electronegative element and is very difficult to polarize. Fluorine can form a very stable bond with hydrogen or carbon (see Section 3.1). The rigidity of the C— F bond causes stiffening of the perfluoroalkane chain and limits interactions with other molecules. Because of their small size, fluorine atoms can shield the perfluorinated carbon atom without steric stresses. Perfluoromethyl or perfluoromethylene groups therefore form compounds with very weak intermolecular forces. As a consequence of weak interactions, perfluoroalkanes are insoluble in common organic solvents. Perfluo-roalkanes are more hydrophobic than hydrocarbons, evidenced by solubility data CF4 is seven times less soluble in water than CH4 [1,2]. Water is almost 7 times less soluble in perfluoroheptane than in heptane on a equal weight basis [3] and 25 times more on a molar basis. 

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