O- Amines =)

Question 1

Explain why 3-aminopentane is a stronger base than ammonia. (2)

Answer 1

• lp on N ↑ available
• ∵ alkyl group = e- pushing –> inductive effect

Question 2

Primary amines can be prepared by the reaction of halogenoalkanes with ammonia or by the reduction of nitriles.
Justify the statement that it is better to prepare primary amines from nitriles rather than from halogenoalkanes. (2)

Answer 2

• further reaction (of 1⁰ amine) needed w/ halogenoalkane
• x further reaction w/ nitriles

OR
- impure product –> low atom economy for halogenoalkane
- single product –> high a.e. for nitriles

Question 3

Phenylamine can be prepared by a process involving the reduction of nitrobenzene using tin and an excess of hydrochloric acid.
C6H5NO2 + 6[H] → C6H5NH2 + 2H2O
Explain why an aqueous solution is obtained in this reduction even though phenylamine is insoluble in water. (1)

Answer 3

C6H5NH2 present as ionic salt

Question 4

Aqueous solutions of ammonia, ethylamine and phenylamine are prepared.
Each solution has the same concentration.
Which is the correct order for the pH values of these solutions? (1)

Answer 4

ethylamine > ammonia > phenylamine

lp on N of phenylamine is delocalised into the ring –> ↓ available to combine with H+

Question 5

The student purified the crude solid product, N−phenylethanamide, by
recrystallisation.
Outline the method that the student should use for this recrystallisation. (4)

Answer 5

1. dissolve in min vol of
2. hot water (/ solvent)
3. allow solution to cool + crystals form
4. filter off pure product under ↓ pressure

Question 6

The reaction to form N−phenylethanamide would happen much more quickly if the student used ethanoyl chloride instead of ethanoic anhydride.
Explain why the student might prefer to use ethanoic anhydride, even though it has a slower rate of reaction. (2)

Answer 6

ethanoyl chloride-
- violent reaction w/ water
- HCl released

Question 7

What type of reaction is used to convert (CH3)3N into the cationic surfactant [(CH3)3N(CH2)15CH3]Cl? (1)
A. Bronsted–Lowry acid-base reaction
B. Nucleophilic addition
C. Nucleophilic addition-elimination
D. Nucleophilic substitution

Answer 7

D