Charge transfer and consecutive kinetics of azide‐anion oxidation at platinum, glassy carbon and carbon anodes in acetonitrile, an analogy to Kolbe synthesis

Abstract

AbstractBy evaluating potential‐shifts and slopes of the anodic polarographic wave which is associated with the azide‐anion oxidation in acetonitrile, standard charge transfer rates for N·3 ⇌ N3 + e− were determined at graphitic carbon, glassy carbon and platinum electrodes. This standard exchange rate decreases from carbon to platinum by more than an order of magnitude. Furthermore the rate constants for the consecutive irreversible radical‐dimerization (2N·3 → N6) and competing addition reaction to olefinsmagnified imagewere evaluated by the same means. Dimerization as well as addition reaction are essentially of heterogeneous nature and are heterogeneously catalyzed at carbon electrodes. They are however of a homogeneous character at platinum electrodes due to a relatively poor adsorbability of azide‐and carbon‐radicals at platinum anodes compared to carbon anodes. — It is this special non‐catalytic nature of platinum anodes which favours typical radical dimerization reactions in Kolbe‐synthesis as well as in anodic radical‐addition‐reactions to olefins.