[{"from": "human", "value": "Generate a molecule based on the given description. The molecule is an alkanesulfonic acid in which the alkyl group directly linked to the sulfo functionality is ethyl. It is a conjugate acid of an ethanesulfonate."}, {"from": "gpt", "value": "[C][C][S][=Branch1][C][=O][=Branch1][C][=O][O]"}]