Michael Addition Reaction

with both lithium and copper, which are made from the combination of an alkyl lithium compound and copper halide (such as iodine, bromine, or chlorine). These become rather “ionic” in character with the R chain being negative and both copper and lithium being positive.

In such cases, the carbon atom associated with the copper lithium compound is nucleophilic and it attaches to the beta-carbon atom on the “far side” of the double bond (that is, the conjugate carbon atom). This will shift the electrons to the electronegative oxygen molecule to make an intermediate enolate. This reaction proceeds as is seen in figure 89:

Figure 88.

MICHAEL ADDITION REACTION

Another conjugate addition reaction takes a ketone and an enone or enal, causing the addition of the ketone to the conjugate carbon atom of the enone or enal. This is done under basic circumstances in order to pull off an alpha hydrogen from the ketone, attaching the ketone that is now effectively negatively charged (nucleophilic) to the conjugate carbon atom, which is slightly electrophilic. It relies on the slight acidity of the alpha carbon next to the carbonyl group. The reaction is otherwise the same as in figure 89 except that it is done under basic conditions with water donating the necessary alpha hydrogen atom to make the molecule saturated rather than a hydrogen ion.