Crotonic acid
IUPAC name	(E)-2-butenoic acid
Other names	trans-2-butenoic acid beta-methylacrylic acid 3-methylacrylic acid
Identifiers
CAS number	107-93-7
SMILES	C/C=C/C(O)=O
Properties
Molecular formula	C4H6O2
Molar mass	86.09 g/mol
Density	1.02 g/cm3
Melting point	70–73 °C
Boiling point	185–189 °C
Solubility in THF, ethanol, methanol	THF 8.09 M, ethanol 6.15 M, methanol 7.62 M [1]
Hazards
MSDS	Sciencelab MSDS
Related compounds
Other anions	crotonate
Related carboxylic acids	propionic acid acrylic acid butyric acid succinic acid malic acid tartaric acid fumaric acid pentanoic acid
Related compounds	butanol butyraldehyde crotonaldehyde 2-butanone
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Crotonic acid, or trans-2-butenoic acid, is a short-chain unsaturated carboxylic acid, described by the formula CH₃CH=CHCO₂H. Crotonic acid is so named because it was erroneously thought to be a saponification product of croton oil. It crystallizes as needles from hot water.

Isocrotonic acid (or quartenylic acid) is the cis analogue of crotonic acid. It is an oil, possessing a smell similar to that of brown sugar. It boils at 171.9 °C, concomitant with conversion into crotonic acid. Isomerizaton is complete when the cis acid is heated to 170–180 °C in a sealed tube.

Racemic threonine can be prepared from crotonic acid by alpha-functionalization using mercury(II) acetate.^[2]

[edit] See also

• Crotyl
• Crotonaldehyde
• Crotyl alcohol
• Methacrylic acid

[edit] References

1. ^ Solubility of crotonic acid in non-aqueous solvents
2. ^ Carter, H. E.; West, H. D. (1955), "dl-Threonine", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv3p0813 ; Coll. Vol. 3: 813 

This article incorporates text from the Encyclopædia Britannica, Eleventh Edition, a publication now in the public domain.