[{"from": "human", "value": "Describe this molecule. [C][=C][Branch1][#C][C][=Branch1][C][=O][O][/C][\\-Ring1][=Branch1][=C][\\C][=Branch1][C][=O][O-1][Cl]"}, {"from": "gpt", "value": "The molecule is the conjugate base of trans-2-chloro-4-carboxymethylenebut-2-en-1,4-olide; major species at pH 7.3. It is a conjugate base of a trans-2-chloro-4-carboxymethylenebut-2-en-1,4-olide."}]