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
References