O2: 28 Amines

Question 1

How can primary amines be prepared?

Answer 1

By the reaction of ammonia with halogenoalkanes and by the reduction of nitriles.

Question 2

How are aromatic amines prepared?

Answer 2

By the reduction of nitro compounds.

Question 3

What are aromatic amines used in?

Answer 3

The manufacture of dyes.

Question 4

What strength base are amines?

Answer 4

Amines are weak bases.

Question 5

What is the difference in base strength between ammonia, primary amines, and aromatic amines?

Answer 5

Aromatic amines < ammonia < primary amines

Question 6

Explain the difference in base strength between ammonia, primary amines, and aromatic amines.

Answer 6

Amines are weak bases because they accept protons due to the lone pair of electrons on the N.
The more available the lone pair on the N is, the more likely the amine is to accept a proton, so the stronger a base it will be.

Primary amines are the stronger base because the alkyl group has a positive inductive effect on the lone pair on the N, making it more available to attract protons.
Aromatic amines are the weakest base because the benzene ring is an area of high electron density which partially delocalises the lone pair on N, making it less available to attract protons.

Question 7

What are amines?

Answer 7

Nucleophiles.

Question 8

Name and outline the reaction mechanism of ammonia/ amines with halogenoalkanes.
What does this produce?

Answer 8

Nucleophilic substitution.
Forms primary, secondary, tertiary amines and quaternary ammonium salts.

Question 9

What are the uses of quaternary ammonium salts?

Answer 9

Used as cationic surfactants.
Used to manufacture fabric and hair conditioners.

Question 10

Name and outline the reaction mechanism of ammonia/ primary amines with acyl chlorides/ acid anhydrides.

Answer 10

Nucleophilic addition-elimination.