24. Enolate Chemistry: Reactions at the Alpha-Carbon

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

(d) nitroacetone

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

(c) pentane-2,4-dione

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

(c) ethyl α-cyanoacetate

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.

(g)

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.

Alkylation of the following compound with methyl iodide under two different conditions forms two different ketoesters (A and B). Each ketoester forms a cyclic diketone (C and D) when treated with methoxide ion in methanol. a. Draw the structures of A and B, and indicate the conditions used in the alkylation reaction that cause that ketoester to be formed.

1. Rank the following compounds in order of increasing acidity.

Identify the enolate(s) that would form on treatment of each of the following carbonyls with base. [When there are two possibilities, draw both.]

(a)