Quiz - Enols, Enolates, Aldol Condensation | Enols, Enolates and Aldol Condensation - Part 1

1

Which of the following reagents can deprotonate a hydrogen on a carbon in the α position of a carbonyl?

Et3N

LDA

NaOH

CH3COO-

H on an α-carbon of a carbonyl has a pKa ~ 16-18 (aldehyde) and ~ 19-21 (ketone). Et3N (pKa = 10.8), NaOH (pKa = 15.7) and CH3COO- (pKa = 4.76) are not strong enough to deprotonate this species unlike LDA (pKa = 36)

2

What is the product of an aldol condensation?

An alkene

A diol

A dicarbonyl

An α,β-unsaturated aldehyde or ketone

3

What is the reactivity of an α,β-unsaturated aldehyde or ketone?

Typical reactivity of alkenes

Typical reactivity of carbonyls

1,4-addition reactions

All of the above

Reactivity of an α,β-unsaturated aldehyde or ketone:
- typical reactions of alkenes and carbonyls
- 1,4-additions (and sometimes 1,2-additions)

4

What is the product of the reaction between water and pent-3-en-2-one?

3-hydroxypentan-2-one

4-hydroxypentan-2-one

Pentane-2,4-diol

Pentane-2,4-dione

5

Which of the following statements about keto-enol equilibrium is correct?

The enol form is less stable than the corresponding keto form

Enol-Keto equilibrium can be catalyzed by a base

Enol-Keto equilibrium can be catalyzed by an acid

All of the above

Carbonyls are in equilibrium with their enol forms (10 kcal.mol-1 less stable). This equilibrium can be catalyzed by a base or by an acid

6

Which of the following molecules is the most acidic?

β-diketone

Ketone

Aldehyde

Ester

β-diketone (pKa = 9) < Aldehyde (pKa ~ 16-18) < Ketone (pKa ~ 19-21) < Ester (pKa ~ 25)