- Source: Semidione
Semidiones are radical anions analogous to semiquinones, obtained from the one-electron reduction of non-quinone conjugated dicarbonyls.
The simplest possible semidiones are derived from 1,2-dicarbonyls and have structure R−C(−O−)=C(−O•)−R', making them the second member of a homologous series starting with ketyl radicals.
They are often transient intermediates, appearing in reactions such as the final reduction step of the acyloin condensation.
Benzil semidione (Ph−C(−O−)=C(−O•)−Ph), synthesized by Auguste Laurent in 1836, is believed to have been the first radical ion ever characterized.
Semidehydroascorbate is a stable semidione produced by the one-electron oxidation of Vitamin C.
