Amines

Question 1

How can primary amines act as bases

Answer 1

• the lone pair of electrons on the nitrogen is readily available for forming a dative covalent bond with the H+ and accepting a proton

Question 2

Why are primary amines stronger bases than ammonia

Answer 2

• The alkyl groups donate electron density to nitrogen
• so make the lone pair more readily available to accept a proton

Question 3

Why are secondary amines stronger bases than primary

Answer 3

• They have more alkyl groups
• so more electrons are pushed to the Nitrogen
• so more positive inductive effect
• lone pair is more available to accept a proton

Question 4

Why are aromatic amines the weakest bases

Answer 4

• if the N is attached to a benzene ring the lone pair on the nitrogen becomes partially delocalised into the ring
• so lone pair on Nitrogen is less available to accept a proton

Question 5

What’s the overall order of base strength weakest to strongest

Answer 5

• aromatic amines (weakest)
• ammonia
• 1° amines
• 2° amines (strongest)

Question 6

How do benzene rings bonded to nitrogen effect lone pair availability

Answer 6

Makes it less available so less likely to accept a proton so weaker base

Question 7

Why is it better to prepare primary amines from nitriles compared to haloalkanes

Answer 7

With haloalkane there is a further reaction but with nitriles there isn’t

Question 8

Describe number of alkyl groups in 1°, 2°, 3°,4° amines

Answer 8

Primary - 1 alkyl group
Secondary - 2 alkyl groups
Tertiary - 3 alkyl groups
Quarternary- 4 alkyl groups

Question 9

What is the difference between aliphatic and aromatic amine

Answer 9

Aliphatic - without benzene
Aromatic - benzene