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' ↔ R−C(−O)=C(−O)−R', making them the second member of a homologous series starting with ketyl radicals and continuing with semitriones. 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 ↔ 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 relatively stable semitrione produced by hydrogen abstraction from ascorbate (Vitamin C).
References
- ^ Russell, Glen A. (1968). "Chapter 3: Semidione Radical Anions". In Kevan, Larry; Kaiser, Emil T. (eds.). Radical Ions. New York Interscience. pp. 87–150. ISBN 978-0-470-45490-9.
- Roth, Heinz D. (2004). "Chapter 6: Organic Radical Ions". In Moss, Robert A.; Platz, Matthew; Jones, Maitland (eds.). Reactive Intermediate Chemistry. Wiley-Interscience. p. 260. ISBN 978-0-471-23324-4.
- Russell, Glen A.; Norris, Robert K. (1973). "Chapter 6: Radical Ions". In McManus, Samuel P. (ed.). Organic Reactive Intermediates. Organic Chemistry. Vol. 26. Elsevier. pp. 423–448. doi:10.1016/B978-0-12-485450-5.50011-7. ISSN 0078-611X.
- Laurent, Auguste (1836), "Benzoyl und Benzimid.", Annalen der Pharmacie, 17 (1): 88–94, doi:10.1002/jlac.18360170116, hdl:2027/mdp.39015026322357
- Njus, David; Kelley, Patrick M.; Tu, Yi-Jung; Schlegel, H. Bernhard (November 2020). "Ascorbic acid: The chemistry underlying its antioxidant properties". Free Radical Biology and Medicine. 159: 37–43. doi:10.1016/j.freeradbiomed.2020.07.013.
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