The electrochemical behaviour of alkanes in fluorosulphonic acid

Abstract

The anodic oxidation of several alkanes in fluorosulphonic acid containing various carboxylic acids has been studied, the product in each case being an αβ-unsaturated ketone. These species can undergo further oxidation and electroanalytical techniques have been used to define the optimum conditions for the formation of the αβ-unsaturated ketones. The oxidation potential for an alkane in fluorosulphonic acid is shown to depend on the proton donating ability of the medium and the nature of this ‘pH’ dependence shows that there is a rapid protonation equilibrium prior to the electron transfer step and that it is the protonated alkane which undergoes oxidation. In addition, in more acid solutions, the alkanes are shown to undergo spontaneous chemical reactions which yield similar products. Possible mechanisms for the chemical and anodic reactions are discussed and it is shown that electroanalytical techniques may be used to investigate the chemistry of alkanes in fluorosulphonic acid. The application of these reactions to synthesis is considered.