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3.2. Bis(perfluoroalkansulfonyl)imides and their use in fluoroorganic synthesis. Most resistant are amides of sulfo-acids. Anionoid and nonionic surfactants are produced from fluoroanhydride of perfluorooctanesulfo acid C8F17SO2F.
Surface active materials containing fluorine are are characterized by high resistance to strong acids and concentrated alkali and they effectively decrease surface tension in such mediums. The synthesis of perfluorinated bis(perfluoroalkansulfonyl)imides is rather difficult task, because here there is the influence of perfluoroalkanesulfonyl group [76-80]. Nevertheless as early as in 1972 the authors of the work [81] had suggested the obtaining method of bis(perfluoroalkansulfonyl)imides by ammonia action on perfluoroalkansulfonyl fluoride. The following compounds were obtained: RFSO2NHSO2RF' ( RF'= CF3, C4F9, C8F17; RF' = C4F9, C8F17). However these authors didn't get the key compound – (CF3SO2)2NH. Later in 1984 DesMarteau with co-workers suggested modified method, which include hexamethylsilazane application [82-89]. This compound was white crystals with melting point 49-50 oC, which evaporates in open air and dissolves exothermally in water. Aqueous solution of this compound is stable. It is a strong acid, which titrate by aqueous solution of NaOH.
Imides with different alkyl groups can be obtained using this method, for example C4F9, C6F13, C8F17 [90].
The acidity of this amide is pK = 7.8, while compare to nitric acid (pK = 10.2) it is higher. It can be explained by resonance stabilization.
The following compounds RFSO2NHSO2RF (R = CF3, C4F9, C6F13),
Polymers and compounds are synthesized on their basis [83,85].
Such polymers are regarded as potential firm polymeric electrolytes for
batteries and rechargeable accumulators [88,89]. The authors [90] had obtained bis(perfluoroalkansulfonyl)imide by the reaction of perfluorooctylsulfonamine and perfluorooctylsulfo fluoride in the presence of triethylamine with following neutralization of ammonium salt by sulphuric acid (10%). The reaction of trifluoromethanesulfochloride (or another RFSO2Cl, RF=C1-6 - linear or ramified perfluoroalkyl [92]) with ammonia at the presence of triethylamine (or trialkylamines, heterocycle and aromatic amines [92]) and LiOH is more preferred alternative. The yield of Li-salt amount to 85% [93,94].
The mixture of trifluoromethanesulfonyl fluoride and trifluoromethanesulfonamide in system chlorobenzene-triethylamine is appropriate too. Trifluoromethanesulfo acid ant it's salts didn't decompose up to 350oC. Another Japan company (Central Glass) used liquid ammonia in reaction with perfluoroalkanesulfonyl halide at the presence of triethylamine as base (T=-40oC)[92]. The 3M Company applied non-nucleophilic base Li2CO3 in the reaction of perfluoroalkanesulfonylamide and perfluoroalkanesulfonyl halide [93,94].
The authors of work [95] used K2CO3 as base in the reaction of perfluoroalkanesulfonyl fluoride with fluorocontaining amines.
It should be noted, that if employ triethyleamine as base in this reaction, that ammonium salt of composed amide 5 is produced.
In work [96] was shown that in the reaction of 2(4-bromophenoxy)tetrafluoroethanesulfonyl fluoride with trifluoromethanesulfonamide at the presence of triethylamine and LiOH the lithium salt of N(trifluoromethanesulfonyl)-2-(4-bromophenoxy)-tetrafluoroethane sulfonimide 7 was obtained.
Further compound 7 was transformed into having multiple bond monomer, which after polymerization produced polimer 8, using for membrane generation. The lithium salt of bis(trifluoromethanesulfonyl)amide with 90% yield was obtained via the reaction of CF3SO2F with Li3N in autoclave (tetrahydrofuran medium, 50oC)[97]. Further these salt gave the polymer 4.
This method open broad opportunities for further application in various branches of techniques [83]. The synthesis of amines and it's salts ( M[R1OSO2NO2SOR2]n, where M=H, ion of alkali element or alkaline-earth metals, Al, Ga, In, Sn, Tl, Pb, As; R1,R2 - fluorocontaining C2-C18 alkyl which can have atoms of oxygen or C=C bond) is based on the reaction of bis(chlorosulfonyl)amine HN(SO2Cl)2 with fluorocontaining alcohol [98]. Having another functional groups surfactants one can produce easily by introduction of perfluorosulfo-acid's fluoroanhydride to nucleophilic reaction. The yields always is more then 80% and the reactions go sufficiently easily. Bis(perfluoroalkansulfonyl)imides
can be applied as intermediate product in synthesis of compounds for
agriculture [99], effective Lewis acids in organic synthesis [101-102]. For
example, bis(perfluoromethanesulfonyl)imide promote the reaction of
allyltrimethylsilane with benzaldehyde and PhCH(OH)CH2CH=CH2 with 93% yield
is formed [101]. The reactions of Both imides (CF3SO2)2H, CF3SO2NHSO2(CF2)3CF3 and tris(trifluoromethanesulfonyl)methane [(CF3SO2)3CH] was effective for graphite's derivative compounds ( CxN(SO2CF3)2 x=37) under the treatment of graphite by K2MnF6 in 48% hydrofluoric acid over a (CF3SO2)2NH [104]. Bis(trifluoromethanesulfonyl)amide was used for synthesis of stable compound of xenon ( Xe[N(SO2CF3)2]2) [105]. It should be noted, that trifluoromethylsilylic derivative
(CF3SO2)2NSiMe3, which produced with 93% yield from the reaction of
(CF3SO2)2NH and CH2=CHCH2SiMe3, is the
excellent catalyst (for example, reactions methacrylate with diens )[106].
More over, (CF3SO2)2NSiMe3 is a
fine agent of trimetylsilylation of carbonyl compounds, nitroalkanes,
carboxylic acids esters [107].
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=12 (Me4Si
standard) [84]. The length of carbon skeleton has a weak influence on
and polymeric
ones of the following type were obtained using this method:
,
-unsaturated
carbonyl substances with allyl-containing species goes similarly, the yield
of corresponding trimethylsilylic ethers is sufficiently high [102].