Fluonnation

The alkane is said to undergo fluonnation chlorination bromination or wdinatwn according to whether X2 is F2 CI2 Bi2 or I2 respectively The general term is halo genation Chlorination and hromination are the most widely used... 

The reactivity of the halogens decreases m the order F2 > CI2 > Br2 > I2 Fluo rme is an extremely aggressive oxidizing agent and its reaction with alkanes is strongly exothermic and difficult to control Direct fluonnation of alkanes requires special equip ment and techniques is not a reaction of general applicability and will not be discussed further... 

Chlorination of alkanes is less exothermic than fluonnation and bromination less exothermic than chlorination Iodine is unique among the halogens m that its reaction with alkanes is endothermic and alkyl iodides are never prepared by lodmation of alkanes... 

By carrying out the reaction at —78°C it is possible to fluonnate 2 2 dimethylpropane to yield (CF3)4C Write a balanced chemical equation for this reaction... 

Fluonnation with Diethylammosulfur Tnfluonde and Related Aminofluoro sulfuranes... 

Elemental Huonne as a Legitimate Reagent for Selective Fluonnation of Orgamc Compounds Fluoroaromatic Compounds Synthesis, Reactions, and Commercial Applications New Aspects of Carbonylations Catalyzed by Transition Metal Complexes Polyfluoroaromatics An Excursion m Carbamon Chemistry ... 

As indicated in equation 2 [5, 6, 7. S], rearranged products are sometimes observed during the addition An extensive study of the fluonnation of diphen-ylacetylenes with fluorine reveals complexproduct mixtures that include rearrange ment products [9]... 

Fluorinatton of graphite with fluorine gives graphite fluorides that have interesting properties, as recently reviewed [63]. Pyridine and its derivatives add elemental fluorine to form unstable N-fluoro adducts [14, 26, 64, 65]. These may decompose to 2-fluoropyndines [65] or be stabilized by treatment with inflate salts to form useful electrophilic fluonnating agents [64]... 

Aryl ketone hydra ones are oxidized and fluonnated by fluorine to give a mixture of mono and difluoro hydrocarbons [74] (equation 10)... 

Although fluonnation of peroxoanions [S2] has been examined, the major emphasis in the fluonnation of oxygenated material is the preparation offhioroxy compounds The simplest, trifluoromethyl hypofluorite, can be prepared almost quantitatively by the action of fluorine on carbonyl fluoride (fluorophosgene) in the presence of various catalysts [Si, 84] Addition of fluorine to trifluoroacetic acid [S5] or its sodium salt [S6] gives rise to FjCF(OF)2 Long-chain fluoroxy compounds can also... 

Xenon difluoride has been used to oxidize a number of antimony compounds [102, 109] in yields ranging from 73 to 98%. Elemental fluorine oxidized tris(pen-tafluorophenyl)stibine to tris(pentafluorophenyl)stibine difluoride in 98% yield [706]. Oxidative fluonnation of stibines has also been accomplished with iodine pentafluoride [707]. 

Pentafluorophenylditelluridc yields 79-80% pentafluorophenyltellunum tri fluoride on treatment with fluorine or xenon difluoride [105] The fluonnated tetravalent tellurium can be further oxidized to hexavalent tellurium with either xenon difluoride [/22] or fluorine [123]... 

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]... 

A variety of reagent combinations add fluorine and sulfur to fluonnated olefins. Typically the olefin is reacted with fluoride ion and a source of electrophilic sulfur, such as sulfur tetrafluonde[757,178,179, 7S0], alkyl or amino sulfur tnfluondes [757, 787],... 

The KF-S reaction presumably involves attack of a fluonnated caibanion on sulfur, whereas the S-Sbp5 reaction may involve electrophilic attack by a cationic sulfur species on the olefin under the strong Lewis acid conditions Electrophilic attack on a fluonnated olefin may also account for formation of a perfluorinated sulfide from reaction of bis(pentafluorophenyl)disulfide with hexafluoropropylene under superacid conditions [IS5] (equation 28)... 

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)... 

Deep fluonnation using the La-Mar technique was carried out on polymers such as polyethylene and polypropylene [M], on polyethers [19, 20, 21], and on polyesters subsequently treated with sulfur Cetrafluoride [22] Deep fluorinations carried out under conditions producing limited fragmentation produced oligomeric perlluoropolyethers from powdered polyethylene oxide [23] Deep fluorinations earned out in the limited presence of molecular oxygen result in the conversion of... 

The simplest method for obtaining selective fluonnation is to conduct reactions under conditions that invigorate the electrophilicity of fluorine In practice this method entails the creation of anionic or strongly nucleophilic reactive centers on substrate molecules while suppressing or reducing the tendency toward radical attack Numerous examples of seleetive fluorine attack on carbanionic, amido and carboxylato species are documented Especially abundant is alpha fluonnation of nitroalkanes in polar solvents [42 43, 44, 45 46] (equations 10-14)... 

Selective fluonnation in polar solvents has proved commercially successful in the synthesis of 5 fluorouracil and its pyrimidine relatives, an extensive subject that will be discussed in another section Selective fluonnation of enolates [47], enols [48], and silyl enol ethers [49] resulted in preparation of a/phn-fluoro ketones, fieto-diketones, heta-ketoesters, and aldehydes The reactions of fluorine with these functionalities is most probably an addition to the ene followed by elimination of fluonde ion or hydrogen fluoride rather than a simple substitution In a similar vein, selective fluonnation of pyridmes to give 2-fluoropyridines was shown to proceed through pyridine difluondes [50]... 

The high reactivity of N-H bonds has also been exploited to produce N-F denvatives without significant substitution on neighbonng C-H bonds, Diethyl-phosphoramidates of ammonia, alkylammes, and a,polar solvents to produce difluoroamine [57], N,N-difluoroalkylamines, and a,to-bis(At,7V-difluoroamino)alkanes [52] Acetamide undergoes fluonnation to give modest yields of N,N difluoroacetatnide and acetyl fluonde when fluorinated... 

The product from fluonnation of sodium acetate is acetyl hypofluorite [64], which IS isolated and characterized [65] The value of this reagent lies in its relative mildness, because it reacts cleanly with most olefins adding the elements of acetoxyl and fluorine [66] Tnfluoroacetyl hypofluorite adds cleanly only to benzylic or electron-rich double bonds... 

Electrochemical fluonnation ot N,N dialkylammo-substituted carboxylic acids as their methyl esters produces the analogous perfluonnated tertiary amine carboxylic acid derivatives in 18-30% yields as well as cyclic amine ethers [JOO]... 

Vanadium pentafluoride replaces benzylic hydrogen by fluonne but also adds fluonne to the aromatic system, giving fluonnated cyclohexadienes and cyclohexenes [5] (equation 5)... 

Up to 20 products with different numbers of fluorine atoms and double bonds have been isolated from the fluonnation of benzene with silver difluoride [d], manganese trifluoride [7], potassium tetrafluoroargentate [d], and potassium hexafluoronickelate [24] The composition of the products depends on the fluorinating agents and on the temperature (Table 1)... 

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