Aldol Dehydration: Enone Synthesis
Start with the big picture
In an aldol condensation, a β-hydroxy carbonyl formed by aldol addition loses water or a related leaving group to produce an enone. Under basic conditions, enolate formation and elimination follow an E1cb pathway; acidic conditions promote dehydration through protonation, water loss, and deprotonation. Conjugation between the new carbon–carbon double bond and the carbonyl stabilizes the product, and the less sterically strained trans (E) enone commonly predominates. Elevated temperature or water removal can favor dehydration. The lesson also distinguishes substrate reactivity, introduces the selective Claisen–Schmidt condensation, and considers competing reactions and product identification. Recognizing these features helps explain how enones are prepared for use in Michael additions, Robinson annulations, and polyene synthesis.
What you'll learn
- Describe how aldol dehydration forms an α,β-unsaturated carbonyl.
- Contrast the E1cb and acid-catalyzed E1 dehydration pathways.
- Explain how conjugation and reaction conditions favor enone formation.
- Identify the substrate pattern used in a Claisen–Schmidt condensation.
- Relate enone formation to selected synthetic applications and product identification.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
