A colorless liquid (C4H6O) gave a negative test for the presence of halogens, sulfur, and nitrogen. However, it did give a positive test with 2,4-dinitrophenylhydrazine. The Schiff's reagent and the Jones reagent both gave negative results. The unknown compound also turned a solution of bromine in methylene chloride colorless. What is the structure and name of the colorless liquid?