Isocrotonic acid
Isocrotonic acid is the cis isomer of crotonic acid. It is an oil, possessing a smell similar to that of brown sugar. It boils at 171.9 °C, concomitant with conversion into crotonic acid. Isomerization is complete when the cis acid is heated to 170–180 °C in a sealed tube.
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.
