Citraconic acid

Citraconic acid is an organic compound with the formula CH₃C₂H(CO₂H)₂. It is a white solid. The alkene is cis. The related trans alkene is called mesaconic acid. It is one of the pyrocitric acids formed upon the heating of citric acid.^[1] Citraconic acid can be produced, albeit inefficiently, by oxidation of xylene and methylbutanols. The acid displays the unusual property of spontaneously forming the anhydride, which, unlike maleic anhydride, is a liquid at room temperature.^[2]

Quick facts Names, Identifiers ...

Citraconic acid

Names
Preferred IUPAC name (2Z)-2-Methylbut-2-enedioic acid
Other names 2-Methylmaleic acid Citraconate Methylmaleic acid cis-Methylbutenedioic acid
Identifiers
CAS Number	498-23-7 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:17626 Y
ChemSpider	553689 Y
DrugBank	DB04734 Y
ECHA InfoCard	100.007.145
EC Number	207-858-7
KEGG	C02226
PubChem CID	643798
UNII	0RQ6CXO9KD Y
CompTox Dashboard (EPA)	DTXSID601019903
InChI InChI=1S/C5H6O4/c1-3(5(8)9)2-4(6)7/h2H,1H3,(H,6,7)(H,8,9)/b3-2- Y Key: HNEGQIOMVPPMNR-IHWYPQMZSA-N Y
SMILES O=C(O)\C=C(/C(=O)O)C
Properties
Chemical formula	C5H6O4
Molar mass	130.099 g·mol−1
Appearance	Monoclinic crystals[1]
Density	1.62 g/cm3[1]
Melting point	~90 °C (decomposition)[1]
Solubility in water	Freely soluble[1]
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H302
Precautionary statements	P264, P270, P301+P312, P330, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

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In the laboratory, citraconic acid can be produced by thermal isomerization of itaconic acid anhydride to give citraconic anhydride, which can be hydrolyzed to citraconic acid.^[3] The required itaconic acid anhydride is obtained by dry distillation of citric acid.