Cis-2-butene

2-Butene is an acyclic alkene with four carbon atoms. It is the simplest alkene exhibiting cis/trans-isomerism (also known as (E/Z)-isomerism); that is, it exists as two geometric isomerscis-2-butene ((Z)-but-2-ene) and trans-2-butene ((E)-but-2-ene).