Glassy carbon perceived as graphitized material. Cathodic charge and reactivity toward alkyl halides. A new concept in surface modifications of carbons

Abstract

Glassy carbon was reported to be efficient in two-electron reductive scission of alkyl halides RX for leading to RH. When organic solvents are used, it is shown that, within the potential range [−1.5V to −3V], the electrochemical process is complicated to a large extend by the progressive alkylation of the carbon surface until the formation of compact films composed of immobilized alkyl groups. It is proposed that behaviour be related to the presence of graphitized zones at the glassy carbon surface. These large zones of sp2 carbons can be transformed under electrochemical charge into nucleophilic belts for reacting towards RXs via a kind of heterogeneous SN2. This interfacial process independently coexists with that governed by electron transfers (ET). Therefore, the nature of the scission (pure electron exchange process) with the transient formation of a radical R, should be re-considered according to the real reactivity of the carbon surface, the electrophilicity of the RX and the applied potential. Additionally, this simple procedure may lead to an efficient way for grafting alkyl links and tagging to their extremity several chemical functions.