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Wikipedia / 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 reactivity

Crotonaldehyde is produced by the aldol condensation of acetaldehyde:

  1. 2 CH3CHO → CH3CH=CHCHO + H2O

Crotonaldehyde is a multifunctional molecule that exhibits diverse reactivity. It is a prochiral dienophile. It is a Michael acceptor. Addition of methylmagnesium chloride produces 3-penten-2-ol.

Uses

It is a precursor to many fine chemicals. A prominent industrial example is the crossed aldol condensation with diethyl ketone to give trimethylcyclohexenone, this can be easily converted to trimethylhydroquinone, which is a precursor to the vitamin E. Other derivatives include crotonic acid, 3-methoxybutanol and the food preservative Sorbic acid. Condensation with two equivalents of urea gives a pyrimidine derivative that is employed as a controlled-release fertilizer.

Trans-crotonaldehyde is commonly used to determine the effective Lewis acidity of Lewis acids, determined from the change in 1H NMR shift of the crotonaldehyde handle on binding to a Lewis acid. Limitations of the method include secondary interactions to the 1H NMR handle obscuring the true effect of the Lewis acid, and weak donor strengths of trans-crotonaldehyde resulting in incomplete Lewis acid-base adduct formation.

Crotonaldehyde has application in the following list of agents: Griseofulvin, Crotoniazide, Tilidine, Sethoxydim, Nicocortonide, Kethoxal & 2-Ethylidene-cis-3-hexenal.

Safety

Crotonaldehyde is a potent irritant even at the ppm levels. It is not very toxic, with an of 174 mg/kg (rats, oral).

See also

References