Perfluoroalkanesulfonic acid resins

Palladium complexes exhibit even higher catalytic activity and produce branched acids preferentially.132 133 The selectivity, however, can be shifted to the formation of linear acids by increasing the phosphine concentration.134 Temperature, catalyst concentration, and solvent may also affect the isomer ratio.135 Marked increase in selectivity was achieved by the addition of Group IVB metal halides to palladium136 and platinum complexes.137 Linear acids may be prepared with selectivities up to 99% in this way. The formic acid-Pd(OAc)2-l,4-bis(diphe-nylphosphino)butane system has been found to exhibit similar regioselectivities.138 Significant enhancements of catalytic activity of palladium complexes in car-bomethoxylation by use of perfluoroalkanesulfonic acid resin cocatalysts was reported.139,140... 

Aromatic sulfonic acid and perfluoroalkanesulfonic acids resins are widely used as ion-exchange resins in water treatment and multiple other industrial applications. In the form of membranes, they are routinely used in electrochemical cells, particularly in electroplating of metals and in battery applications. The lithium salts of trifluoromethanesulfonic acid and N-trifluoromethanesulfonyl trifluoromethanesulfonamide are both employed as electrolytes in secondary battery applications. 

Perfluoroacylbenzene sulfonates, 12 174 Perfluoroacyl fluorides, 11 865 alkylation of, 11 883 Perfluoroalkanesulfonic acids, 12 191 Perfluoroalkoxy (PFA) fluorocarbon resins, 18 329... 

The ionic groups (-SO3H) form clusters in the chemically stable Teflon-like matrix (-CF2CF2-) [6]. These hydrophilic domains form micelles, surrounded by the hydrophobic fluorocarbon backbone and connected by small channels. The Nafion resin is prepared as a copolymer of tetrafluoroethylene and perfluoro-2-(fluorosul-fonylethoxy)propyl vinyl ether [1,7]. Unlike other resinsulfonic acids, e. g. sulfo-nated polystyrenes (Dowex-50, Amberlyst-15, Amberlite IR-112, etc.), Nafion and related perfluoroalkanesulfonic acids are stable in corrosive environments and the maximum operating temperature is up to 473K [8]. 

Perfluoroalkanesulfonic acids are mainly prepared by two methods. The first method based on electrochemical fluorination (ECF) in anhydrous hydrogen fluoride (AHF) is the most practical. Although fluorination of the alkanesulfonic acids cannot be carried out directly by ECF9,10, the alkanesulfonyl fluorides can be successfully fluorinated with fairly high yields. The prefluorinated sulfonyl fluoride produced may then be converted to the corresponding salt by alkaline hydrolysis. The free acids were obtained either by their distillation from a solution of the alkaline metal sulfonate in concentrated sulfuric acid or by treatment of the salt with strong acid-type ion exchange resin (equation 1). 

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