Advanced Topic 841 of 1102 Organic Chemistry
Claisen Condensation
Ester enolate attacks another ester giving a beta-keto ester.
In-depth explanation of Claisen Condensation
The Claisen condensation joins two ester molecules in the presence of an alkoxide base to form a beta-keto ester and an alcohol. One ester is deprotonated at its alpha carbon to form an enolate, which attacks the carbonyl of the second ester. The alkoxide leaving group is expelled, giving the beta-keto ester. The reaction requires at least one alpha hydrogen and a full equivalent of base, because the beta-keto ester product is more acidic than the starting ester and its deprotonation drives the equilibrium forward.
Going deeper: Claisen Condensation
Key ideas: Two esters with alpha hydrogens condense using alkoxide base (matching the ester alkoxy group to avoid transesterification) to give a beta-keto ester, with the loss of alcohol. Needs a full equivalent of base because the product beta-keto ester (pKa about 11) is deprotonated, which drives the reaction. Dieckmann condensation is intramolecular and forms 5- or 6-membered rings. Crossed Claisen works when one ester has no alpha hydrogens.
Common mistakes and connections: Students use catalytic base, which fails, or hydroxide, which saponifies. Another error is expecting a product from an ester without alpha hydrogens by itself. Links to aldol, enolate chemistry, acetoacetic ester synthesis and fatty acid biosynthesis.
Visualization of Claisen Condensation
Enolate attack on a second ester, loss of alkoxide, and deprotonation of the product beta-keto ester drives the reaction forward. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Two molecules of ethyl acetate condense with sodium ethoxide to give ethyl acetoacetate.
Frequently asked questions about Claisen Condensation
What is Claisen Condensation?
Ester enolate attacks another ester giving a beta-keto ester.
Is Claisen Condensation a beginner, intermediate or advanced topic?
Claisen Condensation is a advanced topic in Organic Chemistry. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before Claisen Condensation?
Study these earlier topics in Organic Chemistry first: Protecting Groups, Diels-Alder Reaction, Wittig Reaction.
What comes after Claisen Condensation?
The next topics in Organic Chemistry are Michael Addition and Pericyclic Reactions.
Can I practise Claisen Condensation with quizzes?
Yes. The interactive lesson includes a self-check question on Claisen Condensation, and the Organic Chemistry quiz draws on every topic in this area.
Where Claisen Condensation fits in Organic Chemistry
Claisen Condensation is topic 113 of 148 in Organic Chemistry.