Organic Electrochemistry. Revised and Expanded

0521821 - ÚFCH JH 2020 RIV US eng M - Část monografie knihy
Ludvík, Jiří
Reduction of Aldehydes, Ketones, and Azomethines.
Organic Electrochemistry. Revised and Expanded. 5th edition. Boca Raton: CRC Press, 2016 - (Hammerich, O.; Speiser, B.), s. 1202-1246. ISBN 978-1-4200-8401-6
Institucionální podpora: RVO:61388955
Klíčová slova: electrochemistry * carbonyl compounds * azomethines
Obor OECD: Electrochemistry (dry cells, batteries, fuel cells, corrosion metals, electrolysis)

Carbonyl compounds (aldehydes, ketones, quinones, and their nitrogen derivatives-oximes
imines, azines, and hydrazones) are broadly electrochemically investigated and thus, hundreds of
contributions and several review articles and chapters were published during the last five decades
(e.g., References 1-4). In this chapter, besides some fundamental information, the stress was given
to more recent results (particularly from the last 15 years) to follow the development in the field. For
classical original papers, please consult the respective contributions by various authors in previous
editions of this monograph [5-9].
For the carbonyl group-due to its ´´lack of electrons´´ (it belongs to the electron-withdrawing
groups [EWG])-reduction is its typical electrochemical process. The (electro)chemical behavior
of carbonyl compou~ds depends strongly on the structure of the rest of the molecule (aliphatic,
olefinic, aromatic, a- or ~- or m-substitution, planarity-electron delocalization, etc.) and on experimental
conditions (protic/aprotic medium, pH, electrode material, presence of other reactant, etc.).
Therefore, reduction potentials of carbonyl derivatives vary in the span of more than 2 V: for example,
p-benzoquinone (-0.4 V) and acetone (-2.5 V).
When only aldehydes or ketones are reduced, the pattern is in principle similar and simple. The
first electron transfer generates anion radical species. This reaction is followed either by another
one-electron reduction accompanied by protonation (a two-electron heterogeneous process) leading
to an alcohol or by coupling (a one-electron process followed by a homogeneous reaction) yielding
a pinacol [10-12] (Scheme 31.1).
The order and potentials (energetics) of individual electron and proton transfers, however,
differ substantially being influenced by the structure and aromaticity of the molecule bearing
the carbonyl group and by experimental conditions. As a consequence, various mechanisms are
involved, various intermediates are participating, and thus, different proportions of alcohol/pinacol
products result...
Trvalý link: http://hdl.handle.net/11104/0306384