In contrast to RFSO,CH,R (1) (R =hydrogen, alkyl and perfluoicalkyl) and &SO,CF,R$ (2), the reactions of difluorJmethy1 perfluoroalkanesulfonates R,SO,CF,H (3) w:th nucleophiles a n inore complicated. Halide inos, X-fX=F, C1, I) and ethanof only aitack :hc alkoxyl carbon atom, cleaving the C-0 bond to give HCFJ (4) and HCF,OEt (5) respectively. Other reagents such as RC0,-(R=CH,, CF,), C,H,Setc. can eithcr attack the carbon or sulfur atom of 3 to give the corresponding products of C-0 and S-0 bond cleavages. More basic nucleophiles RO-(R=C,H,, Et) mainly abstract the proton of the HCF, moiety to produce difluorosarbene. Ether and benzenc, which can be alkylated by methyl perfluoroalkanesulfoiiate, do not react with 3 under similar conditions. "he reaction rate of 3 with KF is much slower tliaii 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 estent the nucleophilic attack on this carbon, but not so completely as in 2 due to the presence of a hydrogen atom.Polyfluoroalicanesulfonic acid, XVTT, 267 temperature of 3 with KF had to be higher than 70°C and 1OO'C with KCl. However with KI 50°C was enough for 3 to react in ethanol yielding HCF,I (4a), CaH50CF,H (5) and a small amount of I,. When the reaction was carried out in monoglyme (MG) and p-DNB was added to the reaction mixture, 4c was the only product. It seems to show that, similar to 2, an accompanying single electron transfer (SET) process may be operating and is followed by the C-0 bond cleavage: t 1,