Electrochemical oxidation of perfluoroalkenes in fluorosulfuric acid

Abstract

The electrochemical oxidation in fluorosulfuric acid has been shown to be an effective and useful method to functionnalize perfluorinated organic compounds, which are generally extremely difficult to oxidize by conventionnal routes.We have already reported such oxidations of primary linear perfluorinated compounds CF3(CF2)nX with X = H, Br, CH2OH, CO2H and SO3H, and of some secondary hydroperfluoroalkanes and cycloalkanes.The present communication deals with the study of the electrochemical behaviour of perfluoroalk-1-enes in fluorosulfuric acid and of the indirect oxidation of such olefins with the peroxide (FSO3)2.Linear and cyclic voltamperometric studies show that perfluorooct-1-ene C6F13CFCF2 is electroactive in FSO3H (E1/2(Cu/Cu)2+ = 2.01 volts) according to an irreversible electrochemical process. Preparative direct electrochemical oxidation leads to bis (fluorosulfato) perfluoroalkanes, ▪The action of the peroxide (FSO3)2 (preliminary prepared by electrochemical oxidation of FSO3H) on the olefin yields these esters in the same proportions, i.e. 25% of the 1-1 adduct (I) and 75% of the 2-1 adduct dimer (II).Such results can be explained by the intervention of the same mechanism, an electrochemical or chemical oxidation of the olefin, in the two cases. This assumption is discussed.