Isoprene or 2-methyl-1,3-butadiene, is a common organic compound

Organic compound

An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

 with the formula CH₂=C(CH₃)CH=CH₂. Under standard conditions it is a colorless liquid. However, this compound is highly volatile because of its low boiling point.

Isoprene (C₅H₈) is the monomer

Monomer

A monomer is an atom or a small molecule that may bind chemically to other monomers to form a polymer; the term "monomeric protein" may also be used to describe one of the proteins making up a multiprotein complex...

 of natural rubber and also a common structure motif to an immense variety of other naturally occurring compounds, collectively termed the isoprenoids.