Perfluoro and polyfluoroalkanesulfonic acid: XVII. Difluoromethyl perfluoroalkanesulfonates and their reactions

In contrast to R F SO 3 CH 2 R(1)(R=hydrogen, alkyl and perfluoroalkyl) and R F SO 3 CF 2 R F ′ (2), the reactions of difluoromethyl perfluoroalkanesulfonates RFSO 3 CF 2 H (3) With nucleophiles are more complicated. Halide inos, X − (X = F, Cl, I) and ethanol only attack the alkoxyl carbon atom, cleaving the CO bond to give HCF 2 X (4) and HCF 2 OEt (5) respectively. Other reagents such as RCO 2 − (R=CH 3 , CF 3 ), C 6 H 5 S − etc . can either attack the carbon or sulfur atom of 3 to give the corresponding products of CO and SO bond cleavages. More basic nucleophiles RO − (R = C 6 H 5 , Et) mainly abstract the proton of the HCF 2 moiety to produce difluorocarbene. Ether and benzene, which can be alkylated by methyl perfluoroalkanesulfonate, do not react with 3 under similar conditions. The reaction rate of 3 with KF is much slower than that of 1 (R = H). All these data seem to indicate that the shielding effect caused by the two fluorine atoms on the methyl carbon in 3 prevents to some extent the nucleophilic attack on this carbon, but not so completely as in 2 due to the presence of a hydrogen atom.