Nature of Organic Electrode Processes

In some cases, the chemistry of reactions prior to the electron transfer step is important, e.g., enolization rearrangements, protonation, and conformational changes in the electrode double-layer field. 

In aqueous and related media, most of the chemistry of organic electrode reactions is concerned with species resulting from the eventual uptake of one electron and one proton or, more usually, two electrons and two protons (in cathodic reactions) and the reverse processes in some anodic reactions. However, in the latter reactions, the formation of radical intermediates as a result of de-electronation may lead to other chemical changes, e.g., in the total oxidation of hydrocarbons to carbon dioxide in aqueous media and in other ways in the Kolbe, Hofer-Moest and Crum Brown-Walker reactions, and some other carbonium ion type rearrangements. 

The uptake (or loss) of electrons and protons usually occurs in successive stejps, possibly coupled with chemical rearrangements (see below), and the order in which these steps proceed is a matter of great importance it can sometimes be elucidated by means of polarography or related techniques, such as cyclic voltammetry. 

In aprotic nonaqueous media, the organic electrochemistry of anodic and cathodic reactions is concerned predominantly with radical-ion chemistry in many cases involving aromatic substances, the radicals are of sufficient stability for them to be characterized spectroscopically by conventional absorption spectrophotometry and by esr spectroscopy. Linear relations are found between the cathodic and anodic half-wave potentials and the ionization potentials or electron affinities determined in the gas phase. The oxidation and reduction potentials can also be related to the theoretically calculated energies of the highest occupied (anodic process) or lowest vacant (cathodic process) molecular orbitals. 

An important and different class of electroorganic reaction is that which may be called electrocatalytic in type. In such cases, the organic molecule undergoes an initial dissociative chemisorption step (or steps) at the electrode 

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