Question

Draw the structures of the organic products of the claisen condensation reaction between ethyl phenylacetate and ethyl benzoate.

Answer 1

The Claisen condensation produces 3-ketoesters. The reaction mechanism can be summarized as follows:

1. Formation of the enolate: this will take place on the alpha-H (or the hydrogens of the alpha-C) to the carbonyl group. A base is needed to take one alpha-H and produce the enolate.
2. The negative charge on the O atom in the enolate moves to create a C=O bond and the alkene double bond attacks the partially positively charged C of the C=O group of the other compound.
3. The product of step 2 will have a negatively charged O atom, the negative charge electrons will move to form another C=O bond and an alcoxide group will be released (generally this alcoxide will act as the base in step 1 as the reaction goes on).

Mechanism and Answer

Note: this reaction requires a lot of attention and care when it's being made in the lab because the enolate can react with the compound it comes from and not with the other compound (in easier words, A forms an enolate that reacts with B, but if the reaction doesn't have a proper handling, the enolate can react with A too).