[{"from": "human", "value": "Design a molecule that meets the criteria outlined in the description. The molecule is an alkene that is heptane which carries a methylidene group at position 3. It has a role as a human metabolite. It is an alkene and a volatile organic compound."}, {"from": "gpt", "value": "[C][C][C][C][C][=Branch1][C][=C][C][C]"}]