Q59E - Organic Chemistry (Mcmurry)

Question

In the mixed Claisen reaction of cyclopentanone with ethyl format, a much higher yield of the desired product is obtained by first mixing the two carbonyl components and then adding a base, rather than by first mixing base with cyclopentanone and then adding ethyl format. Explain.

Step-by-Step Solution

Answer

Claisen condensation reaction occurs at a much faster rate without any competition with the self-aldol reaction when we add ethyl format first.

Claisen condensation

Claisen condensation occurs between two ester compounds in the presence of a strong base which gives 𝛃- keto ester product and alcohol generally.

The reason for the above case:

If we add base first then cyclopentanone can undergo self-aldol condensation and does not give desired product but when we add ethyl format first then the self-aldol condensation does not occur and it gives a mixed Claisen condensation reaction with a much faster rate without any competition with self-aldol reaction.