Concept:Alkadienes are open-chain hydrocarbons containing two carbon-carbon double bonds.Explanation:Isoprene is chemically 2-methylbuta-1,3-diene, which has two double bonds. So it is an alkadiene.But-2-ene and pent-1-ene both contain only one double bond, so they are alkenes, not dienes.β-Phellandrene is a cyclic monoterpene, not an open-chain alkadiene.Hence, isoprene is the correct alkadiene molecule.
