Propiolic acid

Propiolic acid is the organic compound with the formula HC₂CO₂H. It is the simplest acetylenic carboxylic acid. It is a colourless liquid that crystallises to give silky crystals. Near its boiling point, it decomposes.

Propiolic acid

Names
Preferred IUPAC name Prop-2-ynoic acid[1]
Other names Propiolic acid Acetylene carboxylic acid Propargylic acid Acetylene mono-carboxylic acid
Identifiers
CAS Number	471-25-0 Y
3D model (JSmol)	Interactive image
Beilstein Reference	878176
ChEBI	CHEBI:33199 Y
ChEMBL	ChEMBL1213530 Y
ChemSpider	9706 N
ECHA InfoCard	100.006.763
EC Number	207-437-8
Gmelin Reference	81893
KEGG	C00804 Y
MeSH	C011537
PubChem CID	10110
UNII	P2QW39G9LZ Y
CompTox Dashboard (EPA)	DTXSID6060050
InChI InChI=1S/C3H2O2/c1-2-3(4)5/h1H,(H,4,5) N Key: UORVCLMRJXCDCP-UHFFFAOYSA-N N InChI=1/C3H2O2/c1-2-3(4)5/h1H,(H,4,5) Key: UORVCLMRJXCDCP-UHFFFAOYAX
SMILES C#CC(=O)O
Properties
Chemical formula	C3H2O2
Molar mass	70.047 g·mol−1
Density	1.1325 g/cm3
Melting point	9 °C (48 °F; 282 K)
Boiling point	144 °C (291 °F; 417 K) (decomposes)
Acidity (pKa)	pka = 1.89 [2]
Hazards
GHS labelling:[3]
Pictograms
Signal word	Danger
Hazard statements	H226, H301, H310, H315, H335
Precautionary statements	P210, P233, P240, P241, P242, P243, P261, P262, P264, P270, P271, P280, P301+P310, P302+P350, P302+P352, P303+P361+P353, P304+P340, P310, P312, P321, P322, P330, P332+P313, P361, P362, P363, P370+P378, P403+P233, P403+P235, P405, P501
Safety data sheet (SDS)	External MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

It is soluble in water and possesses an odor like that of acetic acid.^[4][5]

Preparation

It is prepared commercially by oxidizing propargyl alcohol at a lead electrode.^[6] It can also be prepared by decarboxylation of acetylenedicarboxylic acid.

Reactions and applications

Exposure to sunlight converts it into trimesic acid (benzene-1,3,5-tricarboxylic acid).^[5] It undergoes bromination to give dibromoacrylic acid. With hydrogen chloride it forms chloroacrylic acid. Its ethyl ester condenses with hydrazine to form pyrazolone.^[5]

It forms a characteristic explosive solid upon treatment to its aqueous solution with ammoniacal silver nitrate.^[5] An amorphous explosive precipitate forms with ammoniacal cuprous chloride.

Propiolates

Propiolates are esters or salts of propiolic acid. Common examples include methyl propiolate and ethyl propiolate.

See also

• Propargyl
• Propargyl alcohol