Figure 7.3. Michael Addition
(a) The base deprotonates the α-carbon, making it a good nucleophile; (b) The carbanion attacks the
double bond, resulting in a Michael addition.This reaction proceeds as shown due to the resonance stabilization of the intermediates. The better
you understand the resonance forms of molecules, the more you will be able to predict the specific
location on a molecule where a reaction will occur.
KINETIC AND THERMODYNAMIC ENOLATES
Given a ketone that has two different alkyl groups, each of which may have α-hydrogens, two forms
of the enolate can form, with the carbon–carbon double bond between the carbonyl carbon and
either the more or less substituted carbon, as shown in Figure 7.4. The equilibrium between these
forms is dictated by the kinetic and thermodynamic control of the reaction. The kinetically
controlled product is formed more rapidly but is less stable. This form has the double bond to the
less substituted α-carbon. As expected, this product is formed by the removal of the α-hydrogen
from the less substituted α-carbon because it offers less steric hindrance. The thermodynamically
controlled product is formed more slowly, but is more stable and features the double bond being
formed with the more substituted α-carbon. Accordingly, this is formed by the removal of the α-
hydrogen from the more substituted α-carbon.