Pyrocitric acid

Aconitic acid

cis-aconitic acid
trans-aconitic acid
Names
IUPAC name Prop-1-ene-1,2,3-tricarboxylic acid
Other names achilleic acid; equisetic acid; citridinic acid; pyrocitric acid, achilleaic acid
Identifiers
CAS Number	499-12-7 Y 585-84-2 (cis) Y 4023-65-8 (trans) Y
ChemSpider	303 (cis)
ECHA InfoCard	100.007.162
PubChem CID	309 (cis and trans)
InChI InChI=1S/C4H8/c1-3-4-2/h3-4H,1-2H3 Y Key: GTZCVFVGUGFEME-UHFFFAOYSA-N Y InChI=1/C6H6O6/c7-4(8)1-3(6(11)12)2-5(9)10/h1H,2H2,(H,7,8)(H,9,10)(H,11,12) Key: GTZCVFVGUGFEME-UHFFFAOYAL
Properties
Chemical formula	C6H6O6
Molar mass	174.11 g·mol−1
Appearance	Colorless crystals
Melting point	190 °C (374 °F; 463 K) (decomposes) (mixed isomers), 173 °C (cis and trans isomers)
Acidity (pKa)	2.80, 4.46 (trans isomer)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
(what is Y ?)
Infobox references

Aconitic acid is an organic acid. The two isomers are cis-aconitic acid and trans-aconitic acid. The conjugate base of cis-aconitic acid, cis-aconitate is an intermediate in the isomerization of citrate to isocitrate in the citric acid cycle. It is acted upon by the enzyme aconitase.

Aconitic acid can be synthesized by dehydration of citric acid using sulfuric acid:

A mixture of isomers are generated in this way.

It was first prepared by thermal dehydration.