Editing Quinone (section)

=== 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>