Propiolic acid

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Propiolic acid
Propiolic acid Structural Formula V.2.svg
Preferred IUPAC name
Prop-2-ynoic acid
Other names
Propiolic acid (no longer recommended[1])
Acetylene carboxylic acid
Propargylic acid
Acetylene mono-carboxylic acid
3D model (JSmol)
ECHA InfoCard 100.006.763
EC Number 207-437-8
MeSH C011537
Molar mass 70.05 g/mol
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]
Safety data sheet External MSDS
Very Toxic T+
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

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, it is soluble in water and possesses an odor like that of acetic acid.[3][4]


It is prepared commercially by oxidizing propargyl alcohol at a lead electrode,[5] it can also be prepared by decarboxylation of acetylenedicarboxylic acid. Propiolic acid synthesis 01.svg

Reactions and applications[edit]

Exposure to sunlight converts it into trimesic acid (benzene-1,3,5-tricarboxylic acid),[4] it undergoes bromination to give dibromoacrylic acid. With hydrogen chloride it forms chloroacrylic acid, its ethyl ester condenses with hydrazine to form pyrazolone.[4]

It forms a characteristic explosive solid upon treatment to its aqueous solution with ammoniacal silver nitrate.[4] An amorphous explosive precipitate forms with ammoniacal cuprous chloride.


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

See also[edit]


  1. ^ Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 748. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
  2. ^
  3. ^ ed, Susan Budavari, (1990). The Merck index an encyclopedia of chemicals, drugs, and biologicals (11. ed., 2. print. ed.). Rahway, NJ: Merck. pp. 7833, 1911. ISBN 9780911910285.
  4. ^ a b c d Wikisource Chisholm, Hugh, ed. (1911). "Propiolic Acid" . Encyclopædia Britannica. 22 (11th ed.). Cambridge University Press. p. 449.
  5. ^ Wilhelm Riemenschneider (2002). "Carboxylic Acids, Aliphatic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a05_235.