5.5- difluoro hydrofluoric acid

Fluorination in the electrophilic 2-, 4-, and 6-positions is effected by substitutions of other halides, and this is normally performed by nucleophilic displacement with fluoride ion <1994HC(52)1>. Hydrofluoric acid can also be used, and in the case of 2,4-dichloro-5-trichloromethylpyrimidine 111, replacement of all five chlorine atoms occurred, to give 2,4-difluoro-5-trifluoromethylpyrimidine 112, which was subsequently hydrolyzed to give 5-tri-fluoromethyluracil 113 <1996JFC(77)93>. 

It is known66 that the hydrofluoric acid-lead tetraacetate reagent leads, with unsaturated steroids, to cis additions of fluorine. This fact suggests that a cis-difluoro adduct (39b, 42b) is the starting point for the ring contractions observed in the preceding examples. 

Selective formation of 2,2,3,3,3-pentafluoropropan-l-ol (1) is achieved using 80% aqueous hydrofluoric acid or hydrogen fluoride/sulfuric acid mixtures.210 Furthermore, hexafluoro-propene reacts selectively under such modified conditions to give 2,3.3,3-tctrafluoro-2-(tri-fluoromethyl)propan-1-ol (2).210 Symmetrical fluoro-containing ethers 3 are obtained by reaction of 1,1-difluoro- or 1,1-dichloroethene, respectively, with 15% paraformaldehyde in hydrogen fluoride (1-chloroethene reacts analogously).204,21 1,212... 

The pol Tners s Tithesis is recommended to be carried out in inert gas atmosphere at temperatures 50-450 °C. If catalysts used are the salts of carbonic or hydrofluoric acids then oligomers appear. Chain length regulators when producing polyesterketones based on difluoro- or dichlorbenzophe-none and bisphenolates of alkali metals and dihydrox5maphthalenes can be the monatomic phenols [251-253],... 

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