Question 1

Which of the following statements best describes the difference between tautomers and resonance forms in carbonyl chemistry?

Accepted Answer

Tautomers are different compounds with atoms arranged differently, while resonance forms are different representations of the same structure.

Question 2

What is the major product when acetone undergoes base-catalyzed aldol condensation followed by heating?

Accepted Answer

$$\mathrm{CH_3COCH=CH_2$} ($$methyl vinyl ketone)

Question 3

Which base is most effective for complete conversion of a ketone to its enolate before alkylation?

Accepted Answer

Lithium diisopropylamide (LDA)

Question 4

In the Hell–Volhard–Zelinsky (HVZ) reaction, what is the role of $$\mathrm{$$PBr_3$$}$$?

Accepted Answer

It converts the carboxylic acid to an acyl bromide, making the alpha hydrogen more acidic.

Question 5

Which product is formed when cyclohexanone is treated with bromine and sodium hydroxide?

Accepted Answer

2-bromocyclohexanone

Question 6

Which of the following best explains why the enolate ion is more nucleophilic at the alpha carbon than at the oxygen?

Accepted Answer

The alpha carbon is less electronegative than oxygen, making it more reactive toward electrophiles.

Question 7

Which of the following is a necessary condition for a successful crossed aldol condensation?

Accepted Answer

Only one reactant should have alpha hydrogens.

Question 8

What is the product of the base-catalyzed aldol condensation of propanal, followed by dehydration?

Accepted Answer

$$\mathrm{CH_3CH=CHCHO} (2-$$methylpent-2-enal)

Question 9

Which of the following best describes the mechanism of acid-catalyzed keto-enol tautomerism?

Accepted Answer

Protonation of the carbonyl oxygen, followed by deprotonation at the alpha carbon.

Question 10

Which product is expected from the Dieckmann condensation of diethyl adipate?

Accepted Answer

A cyclic $$\beta-$$keto ester (specifically, ethyl cyclopentanone-2-carboxylate)

Question 11

Which of the following is the major product when acetone is treated with LDA followed by allyl bromide?

Accepted Answer

$$\mathrm{CH_2$=CHCH_2COCH_3} ($$allylated acetone)

Question 12

Which of the following statements about the Claisen condensation is correct?

Accepted Answer

It involves the condensation of two esters or one ester and one ketone to form a $$\beta-$$keto ester or $$\beta-$$diketone.

Question 13

Which of the following best explains why dehydration of aldol products is favored upon heating?

Accepted Answer

The formation of a conjugated $$\alpha,\beta-$$unsaturated carbonyl compound is thermodynamically favored.

Question 14

Which of the following is a plausible reason why ring closure to a cycloheptenone is not favored in the intramolecular aldol condensation of octane-2,7-dione?

Accepted Answer

Seven-membered rings have higher ring strain compared to five- or six-membered rings.

Question 15

Which of the following is the correct mechanism for the base-catalyzed alpha halogenation of a ketone?

Accepted Answer

Deprotonation at the alpha carbon to form an enolate, followed by nucleophilic attack on the halogen.

Question 16

Which of the following is the major product of the self-condensation of ethyl phenylacetate with sodium ethoxide?

Accepted Answer

A $$\beta-$$keto ester

Aldol and Related Condensations: Enolate Chemistry and Synthetic Applications

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