Perfluoroalkyls

Perfluoroalkyl derivatives have important technical uses, e.g. sulphonic acids as surfactants introduction of perfluoroalkyl groups confers useful properties on many drugs. 

Particularly alkyl halides which have a perfluoroalkyl group at the /3-position undergo smooth carbonylation. Probably the coordination of fluorine to form a five-membered chelate ring accelerates the reaction. Double carbonylation to give the a-keto amide 915 is possible in Et NH with the fluorine-bearing alkyl iodide 914[769,770]. The ester 917 is obtained by the carbonylation of the /3-perfluoroalkyl iodide 916 in ethanol. 

The reaction of perfluoroalkyl iodides with alkenes affords the perfluoro-alkylated alkyl iodides 931. Q.a-Difluoro-functionalized phosphonates are prepared by the addition of the iododifluoromethylphosphonate (932) at room temperature[778], A one-electron transfer-initiated radical mechanism has been proposed for the addition reaction. Addition to alkynes affords 1-perfluoro-alkyl-2-iodoalkenes (933)[779-781]. The fluorine-containing oxirane 934 is obtained by the reaction of allyl aicohol[782]. Under a CO atmosphere, the carbocarbonylation of the alkenol 935 and the alkynol 937 takes place with perfluoroalkyl iodides to give the fluorine-containing lactones 936 and 938[783]. 

Hydroxy-4-methylthiazole failed to react when submitted to Friedel-Crafts benzoylation conditions (349) on the other hand, it reacted normally in Gattermann and in Reimer-Tiemann formylation reactions, affording the 5-formyl derivative (348). 4-Methylthiazole is insufficiently activated and fails to react under the same conditions. 2,4-Dimethylthiazole undergoes perfluoroalkylation when heated at 200° for 8 hr in a sealed tube with perfluoropropyl iodide and sodium acetate (116) (358). 

ECF is successfully used on a commercial scale to produce certain perfluoroacyl fluorides, perfluoroalkylsulfonyl fluorides, perfluoroalkyl ethers, and perfluoroalkylamines. The perfluoroacyl fluorides and perfluoroalkylsulfonyl fluorides can be hydrolyzed to form the corresponding acid and acid derivatives. Examples include perfluorooctanoyl fluoride [335-66-0] perfluorooctanoic acid [335-67-1] perfluorooctanesulfonyl fluoride [307-35-7] perfluorooctanesulfonic acid [763-23-1] and tris(perfluoro- -butyl)amine [311-89-7]. 

Fluorocarbons are made commercially also by the electrolysis of hydrocarbons in anhydrous hydrogen fluoride (Simons process) (14). Nickel anodes and nickel or steel cathodes are used. Special porous anodes improve the yields. This method is limited to starting materials that are appreciably soluble in hydrogen fluoride, and is most useflil for manufacturing perfluoroalkyl carboxyflc and sulfonic acids, and tertiary amines. For volatile materials with tittle solubility in hydrofluoric acid, a complementary method that uses porous carbon anodes and HF 2KF electrolyte (Phillips process) is useflil (14). 

The higher molecular weight petfluoroalkyl iodides ate prepared by telomerization of tetrafluoroethylene with lower molecular weight perfluoroalkyl iodides (46,48). 

Perfluorinated carboxylic acids are corrosive liquids or solids. The acids are completely ionized in water. The acids are of commercial significance because of their unusual acid strength, chemical stabiUty, high surface activity, and salt solubiUty characteristics. The perfluoroaLkyl acids with six carbons or less are hquids the higher analogues are soHds (Table 1). 

Many of the perfluoroaLkyl carboxyUc acids were first prepared by the electrochemical fluorination (ECF) of the corresponding carboxyUc acids (7). In ECF acid chlorides are converted to the corresponding perfluoroacid fluorides as shown in equation 1 for octanoyl chloride. 

Aromatic perfluoroaLkylation can be effected by fluorinated aUphatics via different techniques. One category features copper-assisted coupling of aryl hahdes with perfluoroalkyl iodides (eg, CF I) (111,112) or difluoromethane derivatives such as CF2Br2 (Burton s reagent) (113,114), as well as electrochemical trifluoromethylation using CF Br with a sacrificial copper anode (115). Extmsion of spacer groups attached to the fluoroalkyl moiety, eg,... 

FLUOROTRIAZINES Riag-fluoriaated triaziaes are used ia fiber-reactive dyes. Perfluoroalkyl triaziaes are offered commercially as mass spectral markers and have been iatensively evaluated for elastomer and hydraulic fluid appHcations. Physical properties of representative fluorotriaziaes are listed ia Table 13. Toxicity data are available. For cyanuric fluoride, LD g =3.1 ppm for 4 h (iahalatioa, rat) and 160 mg/kg (skin, rabbit) (127). 

Solutions of fluorosihcones impart oil and water repeUent finishes to nylon—cotton fabrics. One series of C-1 through C-9 perfluoroalkyl substituents with varying stmctures were attached to siHcon through amide or ether linkages. The fluorosihcones having perfluorinated straight-chain... 

Synthetic oils have been classified by ASTM into synthetic hydrocarbons, organic esters, others, and blends. Synthetic oils may contain the following compounds diaLkylben2enes, poly(a-olefins) polyisobutylene, cycloaUphatics, dibasic acid esters, polyol esters, phosphate esters, siUcate esters, polyglycols, polyphenyl ethers, siUcones, chlorofluorocarbon polymers, and perfluoroalkyl polyethers. 

Alkylated aromatic lubricants, phosphate esters, polyglycols, chlorotrifluoroethylene, siUcones, and siUcates are among other synthetics that came into production during much that same period (28,29). Polyphenyl ethers and perfluoroalkyl polyethers have followed as fluids with distinctive high temperature stabiUty. Although a range of these synthetic fluids find appHcations which employ their unique individual characteristics, total production of synthetics represent only on the order of 2% of the lubricant market. Poly(a-olefin)s, esters, polyglycols, and polybutenes represent the types of primary commercial interest. 

Perfluoroalkyl ether greases thickened with polytetrafluoroethylene (MIL-G-38220 and MIL-G-27617) are used from —40 to 200°C in missiles, aircraft, and appHcations where fuel, oil, and Hquid oxygen resistance is needed (55). Polyphenyl ether greases find special use from 10 to 315°C in high vacuum diffusion pumps and for radiation resistance. 

Fluorochemicals repel both water and oU because they produce an extremely low energy surface (18—26). The effectiveness of the fluorochemicals depends upon uniform surface coverage and orientation of the molecules on the fiber surface so that the perfluoroalkyl chains are directed away from the surface. The result is a GST as low as 5—10 mN /m (dyne/cm). Fluorochemical finishes are often formulated with nonfluorinated resin-based water-repeUent extenders. These water repeUents not only reduce the cost of the finish but may also improve durabUity (27,28). 

Oil Repellent. Fluorochemicals are the only class of material that can provide oil repeUency without altering the porosity of the paper or paperboard. Physical barriers to oil penetration are used primarily for their moisture- or gas-barrier properties, with retarded oil penetration as a secondary benefit. The most common od-repeUent additives are long-chain perfluoroalkyl phosphate salts of ammonia or diethanol amine. Commercial sources include Scotchban (3M), Zonyl (DuPont), and Lodyne (Ciba Specialties). There are also a fluorochemical carboxylate salt, Lodyne (Ciba Specialties), and fluorochemical copolymers, eg, Scotchban (3M). The widest range of oily fluid holdout is provided by the fluorochemical copolymers. 

The fluoroalkyl hypochlorites readily react with GO and SO2 to form the corresponding chloroformates and chlorosulfates in near quantitative yields (270). They add to olefins giving a-chloroethers (271). Borate esters are obtained by reaction of perfluoroalkyl hypochlorites with BGl (272). 

Alkyl-5-arylisoxazoles (303) were prepared by the regiospecific reaction of appropriate 1,3-diketones (302) (R = alkyl or perfluoroalkyl) with hydroxylamine hydrochloride in pyridine (79MI41601). 

PFA Tetrafluoroethylene-perfluoroalkyl (usually propyl) vinyl ether copolymers ... 

Dabroski [123] reported the use of waterbased release coatings based on blends of a small amount of a perfluoroalkyl-alkyl acrylate polymer with a film forming... 

Recent Progress in Perfluoroalkylation by Radical Species with Special Reference to the Use of Bis(perfluoroalkanoyl)peroxides Yoshida, M, Kamigata, N J Fluorine Chem 49, 1-20 62 an c -I d... 

Polymer-bound phenyliodine difluoride, which also has been used as a reagent to add fluorine to alkenes, can be prepared by the addition of xenon difluoride to the polymer [134, 135 136] Methyl iodide is converted to trifluoro methyliodine difluoride by treatment with fluorine at -110 C [137] Perfluoro-alkyliodine tetrafluorides could be synthesized from the perfluoroalkyliodine difluorides and fluorine [138] or chlorine trifluoride [139] Perfluoroalkyl [140] and perfluoroaryl [141] iodides are oxidized to the corresponding iodine difluorides by chlorine trifluoride. 

Additions of halogen fluorides to the more electrophilic perfluonnated olefins generally require different conditions Reactions of iodine fluoride, generated in situ from iodine and iodine pentafluoride [62 102 103, /05] or iodine, hydrogen fluoride, and parapeiiodic aud [104], with fluormated 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 perfluonnated olefins are also known [lOti]... 

Other well-known reactions are those offluorinated olefins with fluoride ion and negatively substituted aromatic compounds leading to the formation of per-fiuoroalkylated aromatic compounds The reaction may be considered an amonic version of a Fnedel Crafts process and can result in introduction of one or several perfluoroalkyl substituents [/ /] Aromatic substrates include substituted and unsuhstiluled perfiuorobenzenes [J3l, 212, 213, 214], fiuorinated heterocycles [131, 203, 215, 216, 217, 218, 219, 220, 221, 222, 223],perchlorinated heterocycles [224] (equation 44), and other activated aromatic compounds [225] (equation 45) The fluonnated olefins can be linear or cyclic [208] (equation 46)... 

Vinyl acetates are also fluormated by mixtures contammg both acyl hy-pofluorite and perfluoroalkyl hypofluorite, obtained from fluorinatton of the carboxylic acid salts [16 19] (equations 20 and 21)... 

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)... 

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