Organic Electrochemical Mechanisms
Published Online: 15 SEP 2006
Copyright © 2000 John Wiley & Sons, Ltd. All rights reserved.
Encyclopedia of Analytical Chemistry
How to Cite
Andrieux, C. P. 2006. Organic Electrochemical Mechanisms. Encyclopedia of Analytical Chemistry. .
- Published Online: 15 SEP 2006
The determination of electrochemical mechanisms by electrochemical techniques is very efficient in organic electrochemistry. In contrast to the electrochemistry of small molecules and ions, the electron transfers on organic compounds are mainly outer-sphere electron transfers following a Marcus–Hush law. Hence these fast electron transfers open up the possibility of obtaining kinetic limitation by the associated homogeneous chemical reactions.
The classical methods for these determinations are stationary techniques such as rotating disk electrode voltammetry (RDEV) and polarography but also more powerful methods, involving large-amplitude transient methods: linear sweep voltammetry (LSV), cyclic voltammetry (CV) and double-step chronoamperometry (DSC) allow the time window to be extended to thousands of microseconds; 1 µs can be reached with the use of ultramicroelectrodes. When the chemical reaction is the rate-determining step, the response, i.e. current as a function of time (or potential), provides information about the nature of this reaction and in many case allows the measurement of its rate constant. Characteristic behaviors are detailed for the principal chemical reactions preceding (C + E) or following (E + C) the electron transfer.
Organic electrochemical mechanisms often involve several electron transfers. The influence of homogeneous electron transfers is underlined in particular for two-electron reductions or oxidations and also in redox catalysis. The possibility of an electron transfer concerted with a chemical reaction is characterized. Some examples of mechanisms and kinetic determinations are given in the field of widely used organic electrosynthetic processes.