Isomers of Butylene

There are four isomers of alkenes which have four carbon atoms and one double bond in their molecules. All four of these hydrocarbons have the same chemical formula ₈, but have different chemical structures. The IUPAC and common names, respectively, of these chemical compounds are:

IUPAC name	common name
1-butene	α-butylene
cis-2-butene	cis-β-butylene
trans-2-butene	trans-β-butylene
methylpropene	isobutylene

The chemical structures are shown at right. The small blue numbers in the structure images are the numbering of the atoms in the main backbone chain of the molecules.

All four of these isomers are gases at room temperature and pressure, but can be liquified by lowering the temperature or raising the pressure on them, in a manner similar to pressurized butane. These gases are colorless, but do have distinct odors, and are highly flammable. Although not naturally present in petroleum in high percentages, they can be produced from petrochemicals. Although they are stable compounds, the carbon-carbon double bonds make them more reactive than similar alkanes, which are more inert compounds in many ways.

Because of the double bonds, these 4-carbon alkenes can act as monomers in the formation of polymers, as well as having other uses as petrochemical intermediates. They are used in the production of synthetic rubber.