But-3-enoic acid

But-3-enoic acid
Names
	Other names vinylacetic acid; allylic acid; 3-butenoic acid; β-butenoic acid;
Identifiers
CAS Number	625-38-7;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:35897;
ChemSpider	30349 ;
ECHA InfoCard	100.009.902
EC Number	210-892-5;
Gmelin Reference	362641
PubChem CID	32743;
CompTox Dashboard (EPA)	DTXSID60211539 ;
	InChI InChI=1S/C4H6O2/c1-2-3-4(5)6/h2H,1,3H2,(H,5,6) Key: PVEOYINWKBTPIZ-UHFFFAOYSA-N;
	SMILES OC(=O)CC=C;
Properties
Chemical formula	C4H6O2
Molar mass	86.090 g·mol−1
Appearance	Clear light yellow liquid
Density	1.013 g/mL
Melting point	−39 °C (−38 °F; 234 K)
Boiling point	163 °C (325 °F; 436 K)
Solubility in water	Well-soluble
Hazards
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H314, H317, H335, H341, H351, H411
Precautionary statements	P202, P273, P280, P303, P304, P305, P310, P338, P340, P351, P353, P361
Related compounds
Related compounds	But-2-ynoic acid; Butenoic acid; Crotonic acid;
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

But-3-enoic acid (or 3-butenoic acid) is a short-chain unsaturated carboxylic acid, with the linear formula CH₂=CHCH₂CO₂H.^[2]

Synthesis

The acid is obtained via a reaction of allyl cyanide and concentrated hydrochloric acid. The mixture is gently heated with occasional shaking. The reaction produces a voluminous precipitate of ammonium chloride. Then water is introduced, and the upper acid layer is separated.^[3]

Other methods are also known.^[4]^[5]

Properties

The acid forms a clear light yellow liquid. Causes skin burns.^[6]

The compound is well-soluble in water, ethanol, and diethyl ether.

Uses

The acid has been employed in preparing specialized coatings and complex organic compounds, including those involving Diels-Alder reactions.^[1]

References

^ ^a ^b "134716 Sigma-Aldrich 3-Butenoic acid". Sigma Aldrich. Retrieved 22 January 2026.
^ "3-Butenoic acid". NIST. Retrieved 22 January 2026.
^ "Vinylacetic Acid". Organic Syntheses. 24: 96. 1944. doi:10.15227/orgsyn.024.0096. Retrieved 22 January 2026.
^ Journal of the Chemical Society. Chemical Society (Great Britain). 1899. p. 736. Retrieved 22 January 2026.
^ Journal of the Chemical Society: Abstracts of papers. 1900. p. 8. Retrieved 22 January 2026.
^ "Vinylacetic acid - Hazardous Agents | Haz-Map". haz-map.com. Retrieved 22 January 2026.

[SA-1] "134716 Sigma-Aldrich 3-Butenoic acid". Sigma Aldrich. Retrieved 22 January 2026.

[2] "3-Butenoic acid". NIST. Retrieved 22 January 2026.

[3] "Vinylacetic Acid". Organic Syntheses. 24: 96. 1944. doi:10.15227/orgsyn.024.0096. Retrieved 22 January 2026.

[4] Journal of the Chemical Society. Chemical Society (Great Britain). 1899. p. 736. Retrieved 22 January 2026.

[5] Journal of the Chemical Society: Abstracts of papers. 1900. p. 8. Retrieved 22 January 2026.

[6] "Vinylacetic acid - Hazardous Agents | Haz-Map". haz-map.com. Retrieved 22 January 2026.

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