Crotonaldehyde

Crotonaldehyde
IUPAC name	(E)-2-Butenal
Other names	Crotonaldehyde crotoinic aldehyde β-Methacrolein
Molecular formula	C4H6O
Identifiers
CAS number	123-73-9
SMILES	O=C/C=C/C
Properties
Molar mass	70.09 g/mol
Density	0.846 g/cm3
Melting point	-76.5 °C
Boiling point	104.0 °C
Solubility in water	organic solvents
Refractive index (nD)	1.4362
Hazards
NFPA 704	3 4 2
R-phrases	11-24/25-26-37/38-41-48/22-50-68
S-phrases	26-28-36/37/39-45-61
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Crotonaldehyde is a chemical compound with the formula CH₃CH=CHCHO. The compound is usually sold as a mixture of the E- and Z-isomers, which differ with respect to the relative position of the methyl and formyl groups. The E-isomer is more common (data given in Table is for the E-isomer). This lachrymatory liquid is moderately soluble in water and miscible in organic solvents. As an unsaturated aldehyde, crotonaldehyde is a versatile intermediate in organic synthesis. It occurs in a variety of foodstuffs, e.g. soybean oils.^[1]

Production and uses

Crotonaldehyde is produced by the aldol condensation of acetaldehyde:

2 CH₃CHO → CH₃CH=CHCHO + H₂O

Its main application is as a precursor to fine chemicals. Sorbic acid, a food preservative, and trimethylhydroquinone, a precursor to the vitamin E, are prepared from crotonaldehyde. Other derivatives include crotonic acid and 3-methoxybutanol.^[1] Crotonaldehyde is a multifunctional molecule that exhibits diverse reactivity. It is an excellent prochiral dienophile.^[2] It is a Michael acceptor. Addition of methylmagnesium chloride affords 3-penten-2-ol.^[3]

Safety

Crotonaldehyde is an irritant. It is listed as an "extremely hazardous substance" as defined by the U.S. Emergency Planning and Community Right-to-Know Act. It occurs widely in nature.

See also

• Crotyl
• Crotonic acid
• Crotyl alcohol
• Methacrolein

References

1. ^ ^{a b} R. P. Schulz, J. Blumenstein, C. Kohlpaintner "Crotonaldehyde and Crotonic Acid" Ullmann's Encyclopedia of Chemical Technology Wiley-VCH, Weinheim: 2005. DOI: 10.1002/14356007.a08 083
2. ^ Longley, Jr., R. I..; Emerson, W. S.; Blardinelli, A. J. (1963). "3,4-Dihydro-2-methoxy-4-methyl-2H-pyran". Org. Synth.; Coll. Vol. 4: 311. 
3. ^ Coburn, E. R. (1955). "3-Penten-2-ol". Org. Synth.; Coll. Vol. 3: 696. 

• Merck Index, 11th Edition, 2599
• Hazardous Substance Fact Sheet