A<unk>  in organic chemistry involves the transfer of an<unk>  from a metal to an organic substrate. It serves to differentiate between true organic<unk> s and other<unk> s such as hydride transfer reactions that actually involve two-electron species.
The first intermediate in a<unk>  is often a radical anion which then engages in secondary reactions. In the Birch<unk>  the secondary reaction is proton abstraction from an alcohol. This reaction type is also called a dissolving metal<unk> . Alkyne<unk>  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<unk><unk>  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<unk>  of ketones to alkanes with zinc-mercury amalgam the intermediate is an organozinc carbenoid.<unk>  rich organic molecules like tetrakis(dimethylamino)ethylene (TDAE) are effective reducing agents capable of generating the anion from alkyl halides such as 5-chloromethyl-6-nitrobenzo[1,3]dioxole 1.
One-electron reduction
Exothermic reaction
Isothermal process
Metabolic intermediate
SN2 reaction
Diradical
Degenerate energy level
Aldol reaction