NEW APPROACHES TO THE STUDY OF ELECTROCHEMICAL DECARBOXYLATION AND THE KOLBE REACTION: PART I. THE MODEL REACTION WITH FORMATE

Abstract

The kinetics of electrochemical decarboxylation of formate ions has been studied in detail for the first time as a model reaction for examination of the decarboxylation and radical coupling that occurs with higher aliphatic acids. Current–potential curves have been obtained which show a sharp transition region, not diffusion controlled, which is characteristic of passivation phenomena. The behavior is observed with gold, palladium, platinum, and gold–palladium alloys. Tafel slopes and exchange currents have been evaluated for the reaction and possible reaction mechanisms are examined in relation to the experimental results.Galvanostatic charging, reverse pulse discharging, and open-circuit decay transients have been obtained which indicate formation of films of adsorbed intermediates on the surface. The transition regions in the current–potential curves are associated with formation of this ad-layer. The galvanostatic results enable distinctions to be made between some of the possible reaction mechanisms proposed and estimates to be made of the extent of film formation by adsorbed intermediates formed in the reaction.