Five isomers that feature the C4H6 molecular formula include 1-butyne, 2-butyne, 1,2-butadiene, 1,3-butadiene and cyclobutene. Other isomers with this formula include methylenecyclopropane, 1-methylcyclopropene, 3-methylcyclopropene and bicyclo[1.1.0]butane. As structural isomers, all of these chemical compounds share the same molecular formula but present differences in terms of structure and chemical properties.
Some of these isomers, such as 1-butyne, 2-butyne, 1,2-butadiene and 1,3-butadiene, are linear isomers, while compounds such as cyclobutene and 1-methylcyclopropene are cyclic isomers. With four atoms of carbon in its structure, butyne is the first compound in the series of alkynes that can feature the triple bond in two different positions, thus forming two different isomers — 1-butyne and 2-butyne.