Decarboxylation 193461 218165113 2008-06-09T13:06:42Z Itub 426390 recat [[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]] &mdash; 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]]