Q: Consider the following reaction: $\ce{CH3COCH3 + CH3CHO \xrightarrow{base} ?}$ What is the major product after dehydration?

$\ce{CH3COCH=CHCHO}$ (\alpha,\beta\text{-unsaturated carbonyl})$

Question 1

Which of the following best explains why the α-hydrogens of aldehydes are generally more acidic than those of ketones?

Accepted Answer

Aldehydes have only one alkyl group, resulting in less electron donation and less steric hindrance, making the α-hydrogens easier to remove.

Question 2

Which of the following conditions would favor formation of the kinetic enolate over the thermodynamic enolate in a reaction involving a ketone with two different α-hydrogens?

Accepted Answer

Low temperature and strong, sterically hindered base

Question 3

A student mixes acetone with benzaldehyde in the presence of a strong base. Which compound acts as the nucleophile in the aldol condensation?

Accepted Answer

Acetone, after deprotonation to form its enolate

Question 4

Which of the following is a tautomeric pair?

Accepted Answer

Imine and enamine

Question 5

Consider the following reaction: $\ce{CH3COCH3 + CH3CHO \xrightarrow{base} ?}$ What is the major product after dehydration?

Accepted Answer

$\ce{CH3COCH=CHCHO}$ (\alpha,\beta	ext{-unsaturated carbonyl})$

Question 6

Which statement about the resonance stabilization of enolate ions is correct?

Accepted Answer

Resonance allows the negative charge to be delocalized between the α-carbon and the carbonyl oxygen.

Question 7

A chemist wants to selectively form the thermodynamic enolate of a ketone. Which set of conditions should they use?

Accepted Answer

High temperature, weak base

Question 8

Which of the following best describes the final product of an aldol condensation after dehydration?

Accepted Answer

$\alpha,\beta$-unsaturated carbonyl

Question 9

In the Michael addition, what role does the enolate ion play?

Accepted Answer

It acts as a nucleophile attacking an α,β-unsaturated carbonyl compound.

Question 10

Which of the following compounds would be most reactive toward nucleophilic attack?

Accepted Answer

Pentanal

Question 11

Which of the following statements about steric hindrance in ketones is correct?

Accepted Answer

Steric hindrance makes ketones less reactive toward nucleophiles than aldehydes.

Question 12

Which of the following is the most acidic hydrogen in the molecule below?

$\ce{CH3COCH2CH2COOH}$

Accepted Answer

The hydrogen on the carboxylic acid group

Question 13

Which of the following is NOT a requirement for a molecule to undergo keto-enol tautomerization?

Accepted Answer

Presence of a leaving group

Question 14

A researcher treats succinaldehyde with lithium diisopropylamide (LDA). What is the immediate result?

Accepted Answer

Formation of a carbanion, increasing nucleophilicity

Question 15

Which of the following best describes the role of the carbonyl oxygen in stabilizing the enolate ion?

Accepted Answer

It withdraws electron density, allowing resonance stabilization of the negative charge.

Question 16

Which of the following reactions is the reverse of an aldol condensation?

Accepted Answer

Retro-aldol reaction

Question 17

Which of the following is a real-world example of an aldol condensation in biological systems?

Accepted Answer

Formation of dihydroxyacetone phosphate and glyceraldehyde 3-phosphate from fructose-1,6-bisphosphate

Question 18

Which of the following statements about enamine formation is correct?

Accepted Answer

Enamines are formed by the tautomerization of imines.

Question 19

Which of the following best describes the equilibrium between keto and enol forms in most carbonyl-containing compounds?

Accepted Answer

The equilibrium favors the keto form because it is more thermodynamically stable.

Kaplan ch 7

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