Isoprene, also known as 2-methyl-1,3-butadiene (CH₂=C(CH₃)CH=CH₂), is a derivative of 1,3-butadiene. Isoprene is a conjugated diene (see Diels-Alder reaction). It is a colorless liquid made by destructive distillation of rubber or from petroleum, and used to make synthetic rubber. It is the basic unit of plant products, including carotenoids, sterols, and terpenes.