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.

Phenylacetone can form two different enols.

(c) Propose mechanisms for the formation of the first enol in base.

Phenylacetone can form two different enols.

(c) Propose mechanisms for the formation of the second enol in acid.

Phenylacetone can form two different enols.

(c) Propose mechanisms for the formation of the second enol in base.

Phenylacetone can form two different enols.

(c) Propose mechanisms for the formation of the first enol in acid.

Show each step in the mechanism of the acid-catalyzed interconversion of (R)- and (S)-3-methylpentan-2-one.

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.

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

(a) acetone

(b) cyclopentanone

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

(c) pentane-2,4-dione

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)

Predict the major products of the following reactions.

Propose a mechanism for the acid-catalyzed reaction of cyclohexanone with pyrrolidine.

Without looking back, propose a mechanism for the hydrolysis of this iminium salt to the alkylated ketone. The first step is attack by water, followed by loss of a proton to give a carbinolamine. Protonation on nitrogen allows pyrrolidine to leave, giving the protonated ketone.

Give the expected products of the following acid-catalyzed reactions.

(a) acetophenone + methylamine

Give the expected products of the following acid-catalyzed reactions.

(b) acetophenone + dimethylamine

Give the expected products of the following acid-catalyzed reactions.

(c) cyclohexanone + aniline

Give the expected products of the following acid-catalyzed reactions.

(d) cyclohexanone + piperidine

Show how you would accomplish each conversion using an enamine synthesis with pyrrolidine as the secondary amine.

(a) cyclopentanone → 2-allylcyclopentanone

(b) pentan-3-one → 2-methyl-1-phenylpentan-3-one

Show how you would accomplish each conversion using an enamine synthesis with pyrrolidine as the secondary amine.

(c)

Propose a mechanism to show how acetophenone undergoes base-promoted chlorination to give trichloroacetophenone.

Propose a mechanism for the reaction of cyclohexyl methyl ketone with excess bromine in the presence of sodium hydroxide.

Predict the products of the following reactions.

(a) cyclopentyl methyl ketone + excess Cl₂ + excess NaOH

(b) 1-cyclopentylethanol + excess I₂ + excess NaOH

(c) propiophenone + excess Br₂ + excess NaOH

Which compounds will give positive iodoform tests?

(a) 1-phenylethanol

(b) pentan-2-one

(c) pentan-2-ol

(d) pentan-3-one

(e) acetone

(f) isopropyl alcohol

Propose a mechanism for the acid-catalyzed bromination of pentan-3-one.

Acid-catalyzed halogenation is synthetically useful for converting ketones to α,β-unsaturated ketones, which are useful in Michael reactions (Section 22-18). Propose a method for converting cyclohexanone to cyclohex-2-en-1-one, an important synthetic starting material.

Show the products of the reactions of these carboxylic acids with PBr₃/Br₂ before and after hydrolysis.

(a) pentanoic acid

(b) phenylacetic acid

(c) succinic acid

(d) oxalic acid

Propose a mechanism for the aldol condensation of cyclohexanone. Do you expect the equilibrium to favor the reactant or the product?

Give the expected products for the aldol condensations of (a) propanal.