Crotonaldehyde is a clear, colorless to straw colored liquid with a strong, suffocating odor. It is highly flammable and produces toxic vapors at room temperature. Crotonaldehyde is found naturally in emissions of some vegetation and volcanoes; many foods contain crotonaldehyde in small amounts.
Crotonaldehyde has the aldehydic group at the C-1 position and −C=C− at the position at C-2 with 4 carbon atoms in the parent chain, thus the name is But-2-en-1-al.
Crotonaldehyde is mainly used in the manufacture of sorbic acid, which is a yeast and mold inhibitor. Crotonaldehyde has been used as a warning agent in fuels, as alcohol denaturant, as stabilizer for tetraethyl-lead, in the preparation of rubber accelerators, and in leather tanning.