[{"from": "human", "value": "Generate a molecule based on the given description. The molecule appears as a colorless crystalline solid. Much more dense than water and insoluble in water. Toxic by ingestion. Vapors are narcotic in high concentration. Used to make other chemicals."}, {"from": "gpt", "value": "[C][Branch1][C][Br][Branch1][C][Br][Branch1][C][Br][Br]"}]