[{"from": "human", "value": "Design a molecule that meets the criteria outlined in the description. The molecule appears as a light-yellow colored liquid that can form a crystalline solid when it dimerizes. Slightly denser than water. Hence sinks in water. Used to make other chemicals."}, {"from": "gpt", "value": "[C][C][Branch1][=Branch1][C][=Branch1][C][=O][C][O]"}]