One-electron reduction
A one-electron reduction in organic chemistry involves the transfer of an electron from a donor compound to an organic substrate. It serves to differentiate between two electron organic reductions such as hydride transfer reactions.
The first intermediate in a one-electron reduction is often a radical anion, which then engages in secondary reactions. In the Birch reduction, the secondary reaction is proton abstraction from an alcohol. This reaction type is also called a dissolving metal reduction. Alkyne reduction to an alkene in the liquid ammonia/sodium system follows the same theme. The first radical anion intermediate abstracts a proton from ammonia to the free radical. A second one-electron transfer leads to the anion, which also abstracts a proton to the neutral alkene.
In the Wurtz reaction, two radical intermediates dimerize in a coupling reaction. Likewise, acetone is converted to pinacol with a magnesium-mercury amalgam in a pinacol coupling reaction. Acyloin condensation couples two carboxylic acids to a α-hydroxyketone. Reactions of this type are also called reductive couplings. In the Clemmensen reduction of ketones to alkanes with zinc-mercury amalgam, the intermediate is an organozinc carbenoid.
Electron rich organic molecules like tetrakisethylene are effective reducing agents capable of generating the anion from alkyl halides such as 5-chloromethyl-6-nitrobenzodioxole:
The one-electron reduction potential of a molecule can be used to obtain an electron affinity. For example: The one-electron reduction potential of molecular oxygen gives a value of 1.07 eV.
Recently, photoredox catalysis has become a very common way to engage in single electron reduction.
