MCAT Organic Chemistry Review

Aldehyde and Ketones II: Enolates

Practice Questions

1.    What is the product of the reaction below?





2.    The reaction below is an example of:

1.    esterification.

2.    tautomerization.

3.    elimination.

4.    dehydration.

3.    Which of the following reactions would produce the compound below?

1.    CH3CHO + CH3CH2CH2CHO →

2.    CH3COCH3 + CH3CH2CH2CHO →

3.    CH3CH2COCH3 + CH3CHO →

4.    CH3CH2CHO + CH3CH2CHO →

4.    Why does the equilibrium between keto and enol tautomers lie far to the keto side?

1.    The keto form is more thermodynamically stable.

2.    The enol form is lower energy.

3.    The enol form is more thermodynamically stable.

1.    I only

2.    III only

3.    I and II only

4.    II and III only

5.    The aldol condensation is an example of which reaction type(s)?

1.    Dehydration

2.    Cleavage

3.    Nucleophilic addition

1.    I only

2.    I and III only

3.    II and III only

4.    I, II, and III

6.    Which of the hydrogens in the following molecule is the most acidic?

1.    A

2.    B

3.    C

4.    D

7.    When reacted with ammonia (NH3) at 200°C, which enolate of a carbonyl-containing compound would predominate?

1.    Kinetic enolate

2.    Thermodynamic enolate

3.    Neither enolate; they would be present in roughly equal proportions

4.    Neither enolate; these reaction conditions would not form either enolate

8.    Which of the following compounds would be most reactive toward a nucleophile?

1.    Pentanal

2.    3-pentanone

3.    Pentane

4.    2-nonanone

9.    α-hydrogens of a ketone are acidic due to:

1.    resonance stabilization.

2.    the electron-withdrawing properties of the alkyl groups.

3.    the electronegative carbonyl oxygen.

1.    I only

2.    I and III only

3.    II and III only

4.    I, II, and III

10.Which of the following is considered a tautomer of the imine functional group?

1.    Cyanohydrin

2.    Hydrazone

3.    Enamine

4.    Semicarbazone

11.When succinaldehyde is treated with lithium diisopropylamide (LDA), it:

1.    becomes more nucleophilic.

2.    becomes less nucleophilic.

3.    generates a carbanion.

1.    I only

2.    II only

3.    I and III only

4.    II and III only

12.Which of the following best describes the final product of an aldol condensation?

1.    1,3-dicarbonyl

2.    1,2-dicarbonyl

3.    α,β-unsaturated carbonyl

4.    β,γ-unsaturated carbonyl

13.When benzaldehyde is reacted with acetone, which will act as the nucleophile?

1.    Benzaldehyde, after addition of strong acid

2.    Benzaldehyde, after reaction with strong base

3.    Acetone, after addition of strong acid

4.    Acetone, after reaction with strong base

14.3-hydroxybutanal can be formed by the reaction of:

1.    methanol in diethyl ether.

2.    ethanal in base, then in acid.

3.    butanal in strong acid.

4.    methanal and ethanal in catalytic base.

15.The catalytic production of dihydroxyacetone and glyceraldehyde 3-phosphate (2-hydroxy-3-oxopropyl dihydrogen phosphate) from fructose-1,6-bisphosphate ({[(2S,3S,4S,5R)-3,4-dihydroxy-5-[(phosphonooxy)methyl]oxolan-2-yl]methoxy}phosphonic acid) is what type of reaction?

1.    Aldol condensation

2.    Retro-aldol reaction

3.    Dehydration

4.    Nucleophilic attack