In organic chemistry, a diene (/ˈd.n/ DY-een) or diolefin (/dˈləfɪn/ dy-OH-lə-fin) is a hydrocarbon that contains two carbon pi bonds. Conjugated dienes are functional groups, with a general formula of CnH2n-2. Dienes and alkynes are functional isomers. Dienes occur occasionally in nature but are widely used in the polymer industry.