Advanced Topic 803 of 1102 Organic Chemistry
Aldol Condensation
Enolates add to carbonyls forming beta-hydroxy carbonyls that dehydrate to enones.
In-depth explanation of Aldol Condensation
The aldol condensation begins when a base removes an alpha hydrogen from an aldehyde or ketone to form an enolate, which then attacks the carbonyl carbon of a second carbonyl molecule. This addition gives a beta-hydroxy aldehyde or ketone called an aldol. On heating, the aldol loses water in an elimination step, giving a conjugated alpha, beta-unsaturated carbonyl compound. The reaction requires at least one alpha hydrogen and is one of the most important carbon-carbon bond forming reactions in organic synthesis.
Going deeper: Aldol Condensation
Key ideas: An aldehyde or ketone with alpha hydrogens gives an enolate with dilute base (NaOH); the enolate adds to another carbonyl to give a beta-hydroxy carbonyl (aldol). Heating dehydrates it to an alpha,beta-unsaturated carbonyl (condensation). Acetaldehyde gives 3-hydroxybutanal then crotonaldehyde. Crossed aldol works best when one partner has no alpha hydrogens (Claisen-Schmidt).
Common mistakes and connections: Students try aldol with benzaldehyde alone, which cannot form an enolate. Another error is forgetting dehydration needs heat, and that the new bond joins the alpha carbon of one molecule to the carbonyl carbon of the other. Links to alpha hydrogen acidity, Cannizzaro as the alternative, and Robinson annulation.
Visualization of Aldol Condensation
Enolate formation, attack on a second carbonyl to give the aldol, then dehydration to the enone make a multi-step energy path. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Two molecules of ethanal give 3-hydroxybutanal, which dehydrates on heating to crotonaldehyde.
Frequently asked questions about Aldol Condensation
What is Aldol Condensation?
Enolates add to carbonyls forming beta-hydroxy carbonyls that dehydrate to enones.
Is Aldol Condensation a beginner, intermediate or advanced topic?
Aldol 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 Aldol Condensation?
Study these earlier topics in Organic Chemistry first: Aldehydes, Ketones, Nucleophilic Addition to Carbonyls.
What comes after Aldol Condensation?
The next topics in Organic Chemistry are Cannizzaro Reaction and Tollens' Test.
Can I practise Aldol Condensation with quizzes?
Yes. The interactive lesson includes a self-check question on Aldol Condensation, and the Organic Chemistry quiz draws on every topic in this area.
Where Aldol Condensation fits in Organic Chemistry
Aldol Condensation is topic 75 of 148 in Organic Chemistry.