Return to Contents  Chapter 18: Enols and Enolates  Ch 18 contents
The Aldol Reaction of Ketones
Aldol reaction of a ketone
Reaction type : Nucleophilic addition

Summary

Study Tip:
Try to recognise the two units that came together and identify the nucleophilic (enolate) portion and the electrophilic (carbonyl) portion.
Recognise the enone that arises from dehydration.

Related Reactions

MECHANISM OF THE ALDOL CONDENSATION OF A KETONE

 

1. MECHANISM OF THE ALDOL REACTION OF A KETONE

Step 1:
First, an acid-base reaction. Hydroxide functions as a base and removes the acidic α-hydrogen giving the reactive enolate.
mechanism of the Aldol condensation of ketones
Step 2:
The nucleophilic enolate attacks the ketone at the electrophilic carbonyl C in a nucleophilic addition type process giving an intermediate alkoxide.
Step 3:
An acid-base reaction. The alkoxide deprotonates a water molecule creating hydroxide and the β-hydroxyketone, the aldol product.

 
2. MECHANISM OF THE DEHYDRATION OF THE ALDOL PRODUCT

 

Step 1:
First, an acid-base reaction. Hydroxide functions as a base and removes an acidic α-hydrogen giving the reactive enolate.

mechanism of the dehydration of an Aldol product
Step 2:
The electrons associated with the negative charge of the enolate are used to form the C=C and displace the leaving group, regenerating hydroxide giving the conjugated ketone.

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© Dr. Ian Hunt, Department of Chemistry, University of Calgary