24. Enolate Chemistry: Reactions at the Alpha-Carbon

Give the important resonance forms for the possible enolate ions of the following:

(d)

Give the important resonance forms for the possible enolate ions of the following:

(e)

Give the important resonance forms for the possible enolate ions of the following:

(f)

Show the resonance forms for the enolate ions that result when the following compounds are treated with a strong base.

(a) ethyl acetoacetate

(b) pentane-2,4-dione

When cis-2,4-dimethylcyclohexanone is dissolved in aqueous ethanol containing a trace of NaOH, a mixture of cis and trans isomers results. Propose a mechanism for this isomerization.

For each molecule shown below,

1. indicate the most acidic hydrogens.

2. draw the important resonance contributors of the anion that results from removal of the most acidic hydrogen.

(d)

For each molecule shown below,

1. indicate the most acidic hydrogens.

2. draw the important resonance contributors of the anion that results from removal of the most acidic hydrogen.

(e)

Phenylacetone can form two different enols.

(a) Show the structures of these enols.

(b) Predict which enol will be present in the larger concentration at equilibrium.

For each molecule shown below,

1. indicate the most acidic hydrogens.

(a)

(b)

(c)