Quiz - Alpha Carbon Chemistry - 1 | Enols and Enolates - Alpha Carbon Chemistry

Organic Chemistry 3 - Quiz - Alpha Carbon Chemistry - 1

1

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

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 the acid catalyzed reaction between Br2 and propanone?

3

What is the product of an aldol condensation?

4

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

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

5

Which of the following statements is incorrect about an enolate ion?

An enolate is a good nucleophile

6

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

7

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

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

8

Which of the following molecules is the most acidic?

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

9

What is the main difference between the products of an aldol addition and an aldol condensation?

Aldol addition stops at the β-hydroxy aldehyde or ketone, while aldol condensation involves further dehydration to yield an α,β-unsaturated aldehyde or ketone, which involves forming a double bond by removing water.