Decarboxylation
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[[Image:Decarboxylation.gif|thumb|181px|Decarboxylation]]
'''Decarboxylation''' is any [[chemical reaction]] in which a [[carboxyl]] group (-COOH) is split off from a compound as [[carbon dioxide]] (CO<sub>2</sub>).
== In biochemistry==
Common [[biosynthesis|biosynthetic]] decarboxylations of [[amino acid]]s to [[amine]]s are:
* [[tryptophan]] to [[tryptamine]]
* [[phenylalanine]] to [[phenylethylamine]]
* [[tyrosine]] to [[tyramine]]
* [[histidine]] to [[histamine]]
* [[serine]] to [[ethanolamine]]
* [[glutamic acid]] to [[GABA]]
* [[lysine]] to [[cadaverine]]
* [[arginine]] to [[agmatine]]
* [[ornithine]] to [[putrescine]]
* [[5-HTP]] to [[serotonin]]
* [[L-DOPA]] to [[dopamine]]
Other decarboxylation reactions from the [[citric acid cycle]] include:
* [[pyruvate]] to [[acetyl coenzyme A|acetyl-CoA]]
* [[oxalosuccinic acid|oxalosuccinate]] to α-[[ketoglutaric acid|ketoglutarate]]
* α-[[ketoglutaric acid|ketoglutarate]] to [[succinyl coenzyme A|succinyl-CoA]].
Enzymes that catalyze decarboxylations are called [[decarboxylase]]s or, more formally, [[carboxy-lyases]] ([[EC number]] 4.1.1).
== In organic chemistry ==
In [[retrosynthesis]], decarboxylation reactions can be considered the opposite of [[homologation reaction]]s, in that the chain length becomes one carbon shorter.
Chemical decarboxylations [[chemical reaction|reactions]] often require extensive heating in high-boiling solvents. [[Copper]] salts are often added as [[catalyst]]s. Heating a carboxylic acid strongly with [[soda lime]] is also able to effect decarboxylation.<ref>{{cite web | url = http://www.chemguide.co.uk/organicprops/acids/decarbox.html | author = Jim Clark | year = 2004 | publisher = Chemguide | title = The Decarboxylation of Carboxylic Acids and their Salts | accessdate = 2007-10-22}}</ref> Heating the product of the [[malonic ester synthesis]] with [[hydrochloric acid]] also affords decarboxylation.<ref>{{cite web | publisher = Organic Chemistry Portal | url = http://www.organic-chemistry.org/namedreactions/malonic-ester-synthesis.shtm | title = Malonic Ester Synthesis | accessdate = 2007-10-26}}</ref> The addition of catalytic amounts of [[cyclohexen-2-one]] has been reported to catalyze the decarboxylation of [[amino acids]].{{Fact|date=October 2007}}
Decarboxylations are especially easy for beta-[[keto acid]]s due to the formation of a cyclic [[transition state]] for instance in [[Knoevenagel condensation]]s.{{Fact|date=October 2007}} The [[Barton decarboxylation]] and [[Hunsdiecker reaction]] are radical reactions.
[[Kolbe electrolysis]] — the electrolysis of salts of carboxylic acids give the decarboxylated dimer products:
:CH<sub>3</sub>COOH → CH<sub>3</sub>COO<sup>−</sup> → CH<sub>3</sub>COO'''·''' → CH<sub>3</sub>'''·''' + CO<sub>2</sub>
:2CH<sub>3</sub>'''·''' → CH<sub>3</sub>CH<sub>3</sub>
This reaction occurs via a radical mechanism as well.<ref>{{cite web | title = Kolbe Electrolysis | publisher = Organic Chemistry Portal | url = http://www.organic-chemistry.org/namedreactions/kolbe-electrolysis.shtm | accessdate = 2007-10-22}}</ref>
==See also==
* [[Oxidative decarboxylation]]
==References==
<references/>
[[Category:Substitution reactions]]
[[cs:Dekarboxylace]]
[[de:Decarboxylierung]]
[[es:Descarboxilación]]
[[fr:Décarboxylation]]
[[it:Decarbossilazione]]
[[nl:Decarboxylering]]
[[ja:脱炭酸]]
[[pt:Descarboxilação]]
[[sv:Dekarboxylering]]
[[zh:脱羧反应]]