Fluonne

Covalent bonding in F2 gives each fluonne eight electrons in its valence shell and a stable electron configuration equivalent to that of the noble gas neon... 

Alkanes spontaneously burst into flame in the presence of elemental fluonne The reaction that takes place between pentane and F2 gives CF4 and HE as the only products... 

Which would you predict to be more shielded the inner or outer protons of [24]annulene" 13 41 F IS the only isotope of fluonne that occurs naturally and it has a nuclear spin of j... 

Polarizability (Section 4 6) A measure of the ease of distortion of the electric field associated with an atom or a group A fluonne atom in a molecule for example holds its electrons tightly and is very nonpolanzable Iodine is very polanz able... 

Fluonne Containing Dyes (Russ ) Fluorocai bons... 

Modem Methods for the Introduction of Fluonne into Organic Molecules An Approach to Compounds with Altered Chemical and Biological Activities... 

Anhydrous hydrogen fluonde Yield based on fluonne The compound is commercially available The compound has considerable vapor pressure... 

In addition, fluonne [97, 98], trifluoromethyl hypofluorite [99, 100], bisftri-fluoromethyOperoxide [100, 101], trifluoromethyl disulfide [100]. and xenon difluoride [102, lOi, 104] react with phosphines to give the corresponding diflu-orophosphoranes in yields ranging from 25% to near quantitative. Phosphites are fluorinated by carbonyl fluoride [95, 96] or 2-hydroperfIuoropropyl azide [f05J (equation 15). 

Many reagents enable the addition fluonne and another element or group across multiple bonds... 

Tnfluoromethyl hypofluonte will fluorinate Schiff bases, giving N,a,a-tn-fluoroatmnes and a-fluoroimines [144] and reacts with diazoketones to give adducts in modest yields [145] (equation 6) At-Substituted aziridines give nng opened products by 1,3 addition of fluonne on nitrogen and trifluoromethoxy on carbon [146] (equation 7)... 

The most important contnbution of this technology to the science of fluonne chemistry has been its ability to probe mechanistic aspects of elemental fluorine attack on organic molecules As has been long accepted fluorine attack on nonaromatic organic molecules is free radical in nature The great oxidizing power of fluonne and... 

Lead tetrafluoride, generated in situ from lead dioxide and hydrogen fluonde, can replace benzylic hydrogen by fluonne [3] Under sirmlar conditions phenol is simultaneously oxidized to 4,4-difluoro-2,5-cyclohexadienone [4 (equations 3 and 4)... 

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

Many fluorinations by electropositive fluorine reagents produce a-fluoro carbonyl compounds as the final result An extensive review exists on the preparation of a-fiuorocarbonyl compounds [101 Also, electropositive reagents are used widely in the preparation of F-labeled radioactive materials required in positron etmssion tomography for biomedical research Excellent reviews are available on fluonne-18 labeling [//, 72]. 

Methods of Introducing Fluonne into Organic Molecules... 

Into a suspension of 8 g of sodium acetate m 400 mL of a solution of 1 part acetic acid and 10 parts fluorotnchloromethane is passed at -75 C a stream of fluonne diluted to 10% with nitrogen The reacuon is stirred with a Vibromixer A solution of 4-methylacetanilide (20 mmol) in a mixture of dichloromethane and fluorotnchloromethane cooled to -75 °C i s added to 20 mmol of acetyl hypofluonte as determined by titration with potassium iodide After 5 min the mixture is poured into water, and the orgamc layer is washed with sodium bicarbonate soluaon and dried over anhydrous magnesium sulfate After concentrauon and column chromatography over silica gel and elution with chloroform, 2-fluoro-4-methylacetanilide IS obtained m 85% yield... 

Side chain fluonnaied aryl isocyanates are an important group of substances used in the manufacture of biologically active compounds The synthetic routes to the meta- and para trifluoromethylphenyl isocyanates permit the chlorine-fluonne exchange with hydrogen fluoride to proceed under moderate conditions and in a virtually quantitative manner (equation 22)... 

The combination of a hydrogen fluoride addition and a chlorine-fluonne displacement converts 1,1 2,2-tetrachloroethylene-l,2 di(isocyanidedichloride)to perfluoro-A, A -dimethylethylenediamine [37] (equation 28)... 

Anhydrous hydrogen fluonde, potassium fluonde, and sodium fluonde have all been used to promote the chlorine-fluonne exchangein tetmchloropyrukizine All three fliionne sources replace the chlonne in position 3 first Both sodium and potassium... 

Perfluoropmacol reacts with sulfur tetrafluonde in an unconventional way instead of replacement of the hydroxyl groups by fluorine, the substitution of four fluonne atoms in the sulfur tetrafluonde molecule with oxygen occurs to give the corresponding spirosulfurane [J6J] (equation 79)... 

The reaction of diethyl tartrate with sulfur tetrafluonde at 25 °C results in replacement of one hydroxyl group, whereas at 100 °C, both hydroxyl groups are replaced by fluonne to form a,a -difluorosuccinate [762] The stereochemical outcome of the fluonnation of tartrate esters is retention of configuration at one of the chiral carbon atoms and inversion of configuration at the second chiral center [163,164, 165] Thus, treatment ofdimethyl(+)-L-tartrate with sulfur tetrafluonde gives dimethyl meso-a,a difluorosuccinate as the final product [163, 164], whereas dimethyl meso tartrate is converted into a racemic mixture of D- and L-a,a -difluorosuccmates [765] (equation 80)... 

Numerous examples of application of DAST for replacement of carbonyl oxygen by fluonne have been reported in the field of carbohydrates [193,194,195] and particularly in the field of s/eroidi [141, 142, 183, 196, 197, 198, 199]... 

Functionalized hydrazine groups can be replaced by fluonne. The first example is the replacement ot tnalkylhydrazine groups in bis(l,2,2-trimethylhydrazmo)meth-ane, a hydrazine acetal, by tnchloroacetyl fluonde to fotm 1,1,2- trimethyl-2-fluoromethylhydrazine in 87% yield [5J]... 

The carbon-fluonne bond is normally resistant to cleavage by zinc metal so that the carbon-chlonne bond in chlorodifluoromethyl ketones is selecnvely reduced The... 

Photochemically induced reduction of alkyl perfluoro carboxylates in hexa-methylphosphoramide (FfMPA) can replace one, two, or (in the case of tn-fluoroacetate) three a-fluonne atoms with hydrogen [7, S] (equation 5) Chlorine-containing fluorocarboxylates preferentially lose a-chlorme and may even lose P-chlorinc in preference to a fluonne [9] (equation 6) Cyclic a-fluoroketones are also defluonnated photochemically [10] (equation 7)... 

Electrochemical reduction of carbon-fliionne bonds occurs at high pH when a carbonyl group is adjacent Polaiographic reduction of a a,a-tnfluoroacetophe-none without loss of fluonne predominates in acidic media to give the alcohol and the corresponding pinacol, whereas reduction of the unprotonated ketone results in hydrogenolysis of the tnfluoromethyl group to form acetophenone as product Il] (equation 8)... 

Examples of the use of lithium aluminum hydride in stereoselective [75] (equation 9), regioselective [16] (equation 10), and product-selective [77](equation 11) displacements of fluonne are available... 

Stereoselective reduction of vmyhc fluonne is also accomplished with tri-butylphosphine [/S] (equation 12)... 

Although isolated fluonne atoms can survive reductions with hthium aluminum hydnde when they are not m a position a to an ester or nitnle group [79] (equauons 63a and 63b), those in an a position arc reducti vely cleaved The milder borohydride reagents convert an a fluorocarboxylate ester to the corresponding alcohol without loss of fluonne [501 (equation 64)... 

PerfluoroaUcenes are converted to vicinal diols when no fluonne atom is present at the double bond Configurational isomers of perfluoroalkenes [29] (equations 20 and 21) are oxidized stereospecifically Perfluorbicyclo[4 3 0]non-1(6) ene gives the corresponding 1,6 diol m a 24% yield upon oxidation with potassium permanganate at 18 °C for 1 h [29]... 

Fluonnated alkenes with one fluonne atom attached to the double bond are converted to a-hydroxyketones by potassium permanganate [30] (equation 22) a-Diketones are formed by permanganate hydroxylation of double bonds flanked by fluonne atoms [31] (equation 23)... 

Boron tribromide replaces fluonne with bromine on tertiary or secondary carbons however, trifluoromethyl groups are inert in this reaction [70] (equation 57). 

Acidic hydrolysis of l-(<3-methoxyphenyl)pentafluoropropene gives o-hy-droxy-2,3,3,3-tetrafluoropropiophenone by hydrolysis of vinylic fluonne and cleavage of the ether to the phenol [4] (equation 4). 

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