巴豆醛，即2-丁烯醛，结构式CH₃CH＝CHCHO。

巴豆醛有顺式和反式两种双键异构体。市售商品为反式异构体，因顺式异构体不稳定。无色透明有窒息性刺激气味液体。露置于空气中或遇光时逐渐变为淡黄色液体，被氧化为巴豆酸。易溶于水，与乙醇、乙醚、苯、甲苯、汽油、煤油完全混溶。有毒，蒸气对呼吸道和眼部有刺激作用，皮肤接触时有灼烧痛感，且为很强的催泪剂。

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.