Chapter 18: Enols and Enolates

Summary

• Reagents : commonly bases such as NaOH or KOH.
• The first step is the formation of the enolate.
• Enolates tend to react with α,β-unsaturated ketones via conjugate addition.
• A conjugate addition with a carbanion nucleophile is known as the Michael reaction or Michael addition.

Related reactions

• Basic Halogenation of aldehydes and ketones
• Alkylation of enolates
• Organocuprate additions
• Aldol condensation

MECHANISM OF THE MICHAEL ADDITION
Step 1: First, an acid-base reaction. Hydroxide functions as a base and removes the acidic α-hydrogen giving the reactive enolate.
Step 2: The nucleophilic enolate attacks the conjugated ketone at the electrophilic alkene C in a nucleophilic addition type process with the electrons being pushed through to the electronegative O, giving an intermediate enolate.
Step 3: An acid-base reaction. The enolate deprotonates  a water molecule recreating hydroxide and the more favourable carbonyl group.

© Dr. Ian Hunt, Department of Chemistry