Editing Quinone (section)

== Reactions ==
Quinones form polymers by formation of hydrogen bonds with ρ-hydroquinone.<ref>{{cite journal |doi=10.1107/S0567740868002451 |title=On the refinement of the crystal structures of phenoquinone and monoclinic quinhydrone |date=1968 |last1=Sakurai |first1=T. |journal=Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry |volume=24 |issue=3 |pages=403–412 |bibcode=1968AcCrB..24..403S }}</ref>
=== Reduction ===
Quinones are [[Oxidizing agent|oxidizing agents]], sometimes reversibly so. Relative to [[benzoquinone]], more strongly oxidizing quinones include [[chloranil]] and [[2,3-Dichloro-5,6-dicyano-1,4-benzoquinone|2,3-dichloro-5,6-dicyano-1,4-benzoquinone]] (also known as DDQ).<ref>{{JerryMarch}}</ref>

The oxidizing power of quinones is enhanced by the presence of acids.<ref>{{Cite journal |last1=Guin |first1=Partha Sarathi |last2=Das |first2=Saurabh |last3=Mandal |first3=P. C. |date=2011-03-16 |title=Electrochemical Reduction of Quinones in Different Media: A Review |journal=International Journal of Electrochemistry |language=en |volume=2011 |pages=e816202 |doi=10.4061/2011/816202 |issn=2090-3529|doi-access=free }}</ref> In acidic conditions, quinone undergoes two-electron and two-proton reduction to [[hydroquinone]].
[[File:QuinoneAcidicReduction.png|center|thumb|class=skin-invert-image|247x247px|Reduction of quinone in an acidic, buffered media into hydroquinone]]

In alkaline conditions, quinones undergo a reversible single-step, two-electron reduction. In neutral conditions, quinones may undergo either a one-proton, two-electron reduction or a two-electron reduction.  In [[aprotic]] media, quinones undergo two-step reduction without protons.<ref>{{Cite journal |last1=René |first1=Alice |last2=Evans |first2=Dennis H. |date=2012-07-12 |title=Electrochemical Reduction of Some o -Quinone Anion Radicals: Why Is the Current Intensity so Small? |url=https://pubs.acs.org/doi/10.1021/jp3038335 |journal=The Journal of Physical Chemistry C |language=en |volume=116 |issue=27 |pages=14454–14460 |doi=10.1021/jp3038335 |issn=1932-7447|url-access=subscription }}</ref> In the first step, a short-lived [[semiquinone]] intermediate is formed. In the second step, the semiquinone is reduced into a quinone dianion.

9,10-Anthraquinone-2,7-disulphonic acid (AQDS) a quinone similar to one found naturally in [[rhubarb]] has been used as a charge carrier in metal-free [[flow battery|flow batteries]].<ref>{{cite journal|title=A metal-free organic-inorganic aqueous flow battery|journal=Nature|date=9 January 2014|volume=505|issue=7482|pages=195–198|doi=10.1038/nature12909|pmid=24402280|bibcode=2014Natur.505..195H|url=https://dash.harvard.edu/bitstream/handle/1/11688785/Nature_paper_website_version.pdf?sequence=4|last1=Huskinson|first1=Brian|last2=Marshak|first2=Michael P.|last3=Suh|first3=Changwon|last4=Er|first4=Süleyman|last5=Gerhardt|first5=Michael R.|last6=Galvin|first6=Cooper J.|last7=Chen|first7=Xudong|last8=Aspuru-Guzik|first8=Alán|last9=Gordon|first9=Roy G.|last10=Aziz|first10=Michael J.|s2cid=4459692}}</ref>

=== Addition ===
Quinones undergo addition reaction to form 1,4-addition products.<ref name=":0">{{Citation |last1=Smith |first1=P. W. G. |date=1969-01-01 |url=https://www.sciencedirect.com/science/article/pii/B9780080129488500103 |work=Aromatic Chemistry |pages=144–175 |editor-last=Smith |editor-first=P. W. G. |publisher=Pergamon |language=en |doi=10.1016/b978-0-08-012948-8.50010-3 |isbn=978-0-08-012948-8 |access-date=2022-11-17 |last2=Tatchell |first2=A. R. |title=Aromatic Alcohols and Carbonyl Compounds |editor2-last=Tatchell |editor2-first=A. R.|url-access=subscription }}</ref> An example of 1,4-addition reaction is the addition of [[hydrogen chloride]] to form chlorohydroquinone:  
[[File:QuinoneAdditionReaction.png|center|thumb|class=skin-invert-image|240x240px|1,4-addition reaction of quinone with hydrogen chloride to produce chlorohydroquinone]]
Quinones can undergo [[Diels–Alder reaction|Diels–Alder reactions]].<ref name=":0" /> The quinone acts as the dienophile and reacts with a diene at a carbon-carbon double bond.

In [[Diels–Alder reaction]]s quinones are used as dienophiles. Historically important [[total synthesis|syntheses]] include [[cholesterol total synthesis|cholesterol]], [[cortisone]], [[total synthesis of morphine and related alkaloids|morphine]], and [[reserpine]].<ref>{{Cite journal |last1=Nawrat |first1=Christopher C. |last2=Moody |first2=Christopher J. |date=2014-02-17 |title=Quinones as Dienophiles in the Diels–Alder Reaction: History and Applications in Total Synthesis |url=https://onlinelibrary.wiley.com/doi/10.1002/anie.201305908 |journal=Angewandte Chemie International Edition |language=en |volume=53 |issue=8 |pages=2056–2077 |doi=10.1002/anie.201305908|pmid=24446164 |s2cid=1362687 }}</ref>