[{"from": "human", "value": "Generate a molecule based on this description. The molecule is an alkane that has 21 carbons and a straight-chain structure. It has been isolated from plants like Periploca laevigata and Carthamus tinctorius. It has a role as a pheromone, a plant metabolite and a volatile oil component."}, {"from": "gpt", "value": "[C][C][C][C][C][C][C][C][C][C][C][C][C][C][C][C][C][C][C][C][C]"}]