Acetylenedicarboxylic acid

Acetylenedicarboxylic acid^[1]

Names
IUPAC name But-2-ynedioic acid
Other names 2-Butynedioic acid
Identifiers
CAS Registry Number	142-45-0 N
ChEBI	CHEBI:30781 Y
ChemSpider	362 Y
InChI InChI=1S/C4H2O4/c5-3(6)1-2-4(7)8/h(H,5,6)(H,7,8) Y Key: YTIVTFGABIZHHX-UHFFFAOYSA-N Y InChI=1/C4H2O4/c5-3(6)1-2-4(7)8/h(H,5,6)(H,7,8) Key: YTIVTFGABIZHHX-UHFFFAOYAA
Jmol-3D images	Image Image
KEGG	C03248 Y
PubChem	371
SMILES C(#CC(=O)O)C(=O)O O=C(O)C#CC(=O)O
Properties
Molecular formula	C4H2O4
Molar mass	114.06 g·mol−1
Appearance	Crystalline solid
Melting point	175 to 176 °C (347 to 349 °F; 448 to 449 K) (decomposes)[2] 180–187 °C (decomposes)[1]
Hazards
R-phrases	R25 R36/37/38
S-phrases	S26 S45
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
N verify (what is: Y/N?)
Infobox references

Acetylenedicarboxylic acid or butynedioic acid is an organic compound (a dicarboxylic acid) with the formula C₄H₂O₄ or HO₂C-C≡C-CO₂H. It is a crystalline solid that is soluble in diethyl ether.

The removal of two protons yields the acetylenedicarboxylate dianion C₄O₄²⁻, which consists only of carbon and oxygen, making it an oxocarbon anion. Partial ionization yields the monovalent hydrogenacetylenedicarboxylate anion HC₄O₄⁻.

The acid was first described in 1877 by Polish chemist Ernest Bandrowski.^[2][3][4] It can be obtained by treating α,β-dibromosuccinic acid with potassium hydroxide KOH in methanol or ethanol. The reaction yields potassium bromide and potassium acetylenedicarboxylate. The salts are separated and the latter is treated with sulfuric acid.^[2]

Acetylenedicarboxylic acid is used in the synthesis of dimethyl acetylenedicarboxylate, an important laboratory reagent. Both the acid and the monobasic salt potassium hydrogenacetylenedicarboxylate KC₄HO₄ are commonly traded as laboratory chemicals.

See also

• Acetylenedicarboxylate decarboxylase
• Oxalic acid
• Acetylenediol

References