Crotonaldehyde


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. 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.

Production and uses

Crotonaldehyde is produced by the aldol condensation of acetaldehyde:
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.
Crotonaldehyde is a multifunctional molecule that exhibits diverse reactivity. It is an excellent prochiral dienophile. It is a Michael acceptor. Addition of methylmagnesium chloride produces 3-penten-2-ol.
The reaction of crotonaldehyde with ethanol then gives kethoxal.
Polyurethane catalyst N,N,N',N'-tetramethyl-1,4-butanediamine is obtained by hydrogenating N,N,N',N'-tetramethyl-1,4-butenediamine which is a reaction product of crotonaldehyde and dimethylamine.

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. It is used to make preservatives.