1.1.2.2- Tetrafluoroethanesulfonic acid

Harmer et al.28,29 have reported the synthesis of 1,1,2,2-tetrafluoroethanesulfonic acid, CF2HCF2SO3H, and 1,1,2,3,3,3-hexafluoropropanesulfonic acid, CF3CFHCF2-SO3H, by the addition of sulfite to fluorinated double bonds [Eq. (2.12)]. The product acids have lower volatility, which makes their handling easier, and are expected to have similar acidity values to those of their fully fluorinated counterparts. In fact, catalytic conversions of a range of transformations were found to be comparable to triflic acid (see Chapter 5). 

Harmer et al.196 used 1,1,2,2-tetrafluoroethanesulfonic acid in the alkylation of para-xylene with 1-dodecene. The silica-embedded catalyst prepared by the sol-gel method showed much higher activity than the neat acid (almost complete conversion in 15 min at 100°C over the sol-gel-derived material versus 10% conversion, using the same molar amounts of acid). Practically no leaching was detected and the catalyst could be recycled with a slight decrease in conversion. It is in sharp contrast with silica-supported triflic acid, which showed much lower activity due to the loss of volatile triflic acid. 

Amorphous and mesostructured Zr02 solid catalysts impregnated with various amounts of triflic acid were tested in the acylation of biphenyl356,357 and toluene358 (with benzoyl chloride and para-toluyl chloride, respectively, nitrobenzene solvent, 170°C and 130°C). All catalysts exhibited lower activity when compared with neat triflic acid. The mesoporous catalysts, however, showed complete selectivity in the formation of para-benzoylbiphenyl. A triflic acid-silica catalyst, in turn, prepared using an aminopropyl-modified silica, showed good characteristics in the solvent-less acetylation of anisole and 2-methoxynaphthalene with acetic anhydride.359,360 The activity of 1,1,2,2-tetrafluoroethanesulfonic acid, either neat or embedded in silica, was found to be similar to that of triflic acid in the acetylation of anisole.196... 

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