Question 1

Which of the following hydrogens is the most acidic in the molecule $$\mathrm{CH_3COCH_2COCH_3}$$?

Accepted Answer

The hydrogen on the central methylene group ($$\mathrm{CH_2$}) $$between the two carbonyls.

Question 2

How many $$\alpha-$$hydrogens are present in the molecule $$\mathrm{CH_3COCH_2CH_3}$$?

Accepted Answer

$$5$$

Question 3

Which compound can undergo base-catalyzed racemization?

Accepted Answer

A ketone with at least one $$\alpha-$$hydrogen.

Question 4

Which compound can undergo halogenation at the $$\alpha-$$position under acidic conditions?

Accepted Answer

A ketone with $$\alpha-$$hydrogens.

Question 5

Which of the following is the most stable enol form for acetylacetone ($$\mathrm{CH_3COCH_2COCH_3}$$)?

Accepted Answer

The enol stabilized by intramolecular hydrogen bonding between the two carbonyls.

Question 6

What is the major product when ethyl acetoacetate reacts with $$\mathrm{LDA}$$ followed by methyl iodide?

Accepted Answer

Alkylation at the $$\alpha-$$carbon to give ethyl 2-methylacetoacetate.

Question 7

In the reaction of acetone with $$\mathrm{NaOH}$$, which product is formed in the aldol condensation?

Accepted Answer

A $$\alpha,\beta-$$unsaturated ketone (aldol condensation product).

Question 8

Which step is the first in the mechanism of base-catalyzed aldol condensation?

Accepted Answer

Deprotonation of the $$\alpha-$$hydrogen to form an enolate ion.

Question 9

Which reagent is best for the selective reduction of an ester to an aldehyde?

Accepted Answer

$$\mathrm{DIBAL-H} at $$low temperature

Question 10

What is the product when a cyclic ketone is treated with $$\mathrm{CH_2N_2}$$?

Accepted Answer

A ring-expanded ketone via diazomethane reaction.

Question 11

Which of the following best describes the role of $$\mathrm{LDA} in $$organic synthesis?

Accepted Answer

It is a strong, non-nucleophilic base used to generate enolates.

Question 12

In the Claisen condensation, which intermediate is formed after the first deprotonation?

Accepted Answer

An enolate ion.

Question 13

Which of the following is a requirement for a molecule to undergo an aldol reaction?

Accepted Answer

It must have at least one $$\alpha-$$hydrogen.

Question 14

What is the product of the reaction of a $$\beta-$$keto ester with $$\mathrm{NaOH}$$ and heat?

Accepted Answer

Decarboxylation to yield a ketone.

Question 15

Which of the following statements about enolate ions is correct?

Accepted Answer

Enolate ions are stabilized by resonance between the oxygen and the $$\alpha-$$carbon.

Question 16

Which of the following reactions is used to synthesize $$\beta-$$diketones?

Accepted Answer

Claisen condensation.

Question 17

What is the major product when a $$\beta-$$keto ester is treated with $$\mathrm{Br_2$} in $$acetic acid?

Accepted Answer

$$\alpha-$$bromination at the $$\alpha-$$carbon.

Question 18

Which of the following is true about the mechanism of the aldol condensation?

Accepted Answer

The reaction involves formation of an enolate, nucleophilic attack on a carbonyl, and dehydration.

Question 19

Which of the following best explains why $$\beta-$$keto esters are more acidic than simple esters?

Accepted Answer

The $$\alpha-$$hydrogen is stabilized by resonance with two carbonyl groups.

Organic Chemistry II: Practice Exam Study Notes – Enolate Chemistry, Carbonyl Reactions, and Mechanisms

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