3.3.11 Amines

Question 1

How can primary amines be prepared? (2)

Answer 1

Reaction of ammonia with halogenoalkanes

Reduction of nitriles

Question 2

What is a primary amine?

Answer 2

Ammonia with one hydrogen atom replaced with an organic group

Question 3

What is a secondary amine?

Answer 3

Ammonia with two hydrogen atoms replaced with organic groups

Question 4

What is a tertiary amine?

Answer 4

Ammonia with three hydrogen atoms replaced with organic groups

Question 5

What is a quaternary ammonium ion?

Answer 5

A tertiary amine with a fourth organic group added

Question 6

What properties do all amines share? (2)

Answer 6

They are weak bases

They are nucleophiles

Question 7

What does the base strength of amines depend on? (2)

Answer 7

The availability of the nitrogen’s lone pair

A lone pair is more available when the electron density is higher

Question 8

Base strength - primary aromatic amines (4)

Answer 8

Weakest bases
Benzene ring draws electrons in
The lone pair is partially delocalised
Electron density on nitrogen decreases

Question 9

Base strength - primary amines (3)

Answer 9

Strong bases
Alkyl groups push electrons onto attached groups
Electron density on nitrogen increases

Question 10

Base strength - ammonia (2)

Answer 10

Between primary amines and aromatic amines

No benzene ring or alkyl groups

Question 11

What are cationic surfactants?

Answer 11

Positively charged compounds which are partly soluble and partly insoluble in water
Used in fabric conditioners and hair products

Question 12

What are quaternary ammonium salts used as? (4)

Answer 12

Cationic surfactants (must have at least one long hydrocarbon chain)
The long hydrocarbon chain is insoluble but binds to non-polar substances
Positively charged head group is soluble in water
Used in detergents as long chain binds to grease, allowing it to be washed away with water

Question 13

How are amines produced from nitriles? (3)

Answer 13

Use strong reducing agent such as LiAlH4 in dry ether
Dilute acid
In industry a metal catalyst (platinum/nickel) at high temperature and pressure is used - catalytic hydrogenation

Question 14

How do amines react with acyl chlorides?

Answer 14

Nucleophilic addition elimination

Question 15

How are aromatic amines produced? (2)

Answer 15

Reduce nitrobenzene + Sn, conc. HCl and reflux to form a salt
Add NaOH to salt to release phenylamine

Question 16

What are aromatic amines used for?

Answer 16

The manufacture of dyes