Ethyl acetoacetate
The organic compound ethyl acetoacetate (EAA) is the ethyl ester of acetoacetic acid. It is a colorless liquid. It is widely used as a chemical intermediate in the production of a wide variety of compounds. It is used as a flavoring for food. Preparation. Ethyl acetoacetate is produced industrially by treatment of diketene with ethanol. The preparation of ethyl acetoacetate is a classic laboratory procedure. It is prepared via the Claisen condensation of ethyl acetate. Two moles of ethyl acetate condense to form one mole each of ethyl acetoacetate and ethanol. Reactivity. Acidity. Ethyl acetoacetate is diprotic: Keto -enol tautomerism. Ethyl acetoacetate is subject to keto-enol tautomerism. In the neat liquid at 33 °C, the enol consists of 15% of the total. Multicarbon building block. Ethyl acetoacetic acid is a building block in organic synthesis since the protons alpha to carbonyl groups are acidic, and the resulting carbanion undergoes nucleophilic substitution. Ethyl acetoacetate is often used in the acetoacetic ester synthesis similar to diethyl malonate in the malonic ester synthesis or the Knoevenagel condensation. A subsequent thermal decarboxylation is also possible. The dianion of ethylacetoacetate is also a useful building block, except that the electrophile adds  to the terminal carbon. The strategy can be depicted in the following simplified form: Ligand. Similar to the behavior of acetylacetone, the enolate of ethyl acetoacetate can also serve as a bidentate ligand. For example, it forms purple coordination complexes with iron(III) salts: Reduction. Reduction of ethyl acetoacetate gives ethyl 3-hydroxybutyrate. Transesterification. Ethyl acetoacetate transesterifies to give benzyl acetoacetate via a mechanism involving acetylketene. Ethyl (and other) acetoacetates nitrosate readily with equimolar sodium nitrite in acetic acid, to afford the corresponding oximinoacetoacetate esters. A dissolving-zinc reduction of these in acetic acid in the presence of ketoesters or beta -diketones constitute the Knorr pyrrole synthesis, useful for the preparation of porphyrins.