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Crotonaldehyde[1]
IUPAC name	(2E)-but-2-enal
Other names	Crotonaldehyde crotoinic aldehyde β-Methacrolein
Identifiers
CAS number	123-73-9 Y
SMILES	O=C/C=C/C
Properties
Molecular formula	C4H6O
Molar mass	70.09 g mol−1
Appearance	Colorless liquid
Density	0.846 g/cm3
Melting point	-76.5 °C, 197 K, -106 °F
Boiling point	104.0 °C, 377 K, 219 °F
Solubility in methanol	12.17 M [2]
Refractive index (nD)	1.4362
Hazards
R-phrases	R11 R24/25 R26 R37/38 R41 R48/22 R50 R68
S-phrases	S26 S28 S36/37/39 S45 S61
NFPA 704	3 4 2
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox 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.^[3]

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.^[3]

Crotonaldehyde is a multifunctional molecule that exhibits diverse reactivity. It is an excellent prochiral dienophile.^[4] It is a Michael acceptor. Addition of methylmagnesium chloride affords 3-penten-2-ol.^[5]

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. ^ Merck Index, 11th Edition, 2599
2. ^ Solubility of crotonaldehyde in methanol
3. ^ ^{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
4. ^ Longley, Jr., R. I..; Emerson, W. S.; Blardinelli, A. J. (1963), "3,4-Dihydro-2-methoxy-4-methyl-2H-pyran", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV4P0311  ; Coll. Vol. 4: 311  
5. ^ Coburn, E. R. (1955), "3-Penten-2-ol", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV3P0696  ; Coll. Vol. 3: 696  

External links

• Hazardous Substance Fact Sheet