Isocrotonic acid

Isocrotonic acid (also known as quartenylic acid; formally named (Z)-2-butenoic acid) is the cis isomer of crotonic acid. It is an oil, possessing an odor similar to that of brown sugar. At its boiling point of 171.9 °C, it converts into crotonic acid. The compound can be prepared from 1,3dibromo-2butanone via the Favorskii rearrangement.

Related compounds
Ethyl isocrotonate can be prepared by semihydrogenation of ethyl tetrolate.

Rudolph Fittig and Hugo Erdmann showed that the γ-phenyl structural analog of isocrotonic acid forms α-naphthol when dehydrated, an observation that provided useful evidence in understanding the nature of naphthalene.


 * (Z)-(C6H5)CH=CHCH2COOH  →   α-naphthol   +   H2O