[{"from": "human", "value": "Design a molecule that meets the criteria outlined in the description. The molecule appears as a colorless liquid. Less dense than water and insoluble in water. Flash point below 0 \u00b0F. Vapors heavier than air. Inhalation of high concentrations may be narcotic. Used to make rubber and plastics."}, {"from": "gpt", "value": "[C][C][C][=C][C][Ring1][Branch1]"}]