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]

Steps in conversion of citric acid to citraconic acid.
Citraconic acid
Names
Preferred IUPAC name
(2Z)-2-Methylbut-2-enedioic acid
Other names
2-Methylmaleic acid
Citraconate
Methylmaleic acid
cis-Methylbutenedioic acid
Identifiers
3D model (JSmol)
3DMet
ChEBI
ChemSpider
DrugBank
ECHA InfoCard 100.007.145
EC Number
  • 207-858-7
KEGG
UNII
  • InChI=1S/C5H6O4/c1-3(5(8)9)2-4(6)7/h2H,1H3,(H,6,7)(H,8,9)/b3-2- checkY
    Key: HNEGQIOMVPPMNR-IHWYPQMZSA-N checkY
  • O=C(O)\C=C(/C(=O)O)C
Properties
C5H6O4
Molar mass 130.099 g·mol−1
Appearance Monoclinic crystals[1]
Density 1.62 g/cm3[1]
Melting point ~90 °C (decomposition)[1]
Freely soluble[1]
Hazards
GHS labelling:
GHS07: Exclamation mark
Warning
H302
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).
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Infobox references

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.

References
  1. Budavari, Susan, ed. (1996), The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals (12th ed.), Merck, ISBN 0911910123
  2. Kurt Lohbeck; Herbert Haferkorn; Werner Fuhrmann; Norbert Fedtke. "Maleic and Fumaric Acids". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a16_053.
  3. R. L. Shriner; S. G. Ford; l. J. Roll (1931). "Citraconic Anhydride and Citraconic Acid". Org. Synth. 28: 28. doi:10.15227/orgsyn.011.0028.
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