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SolutionsReactivity

1. Complete the reactions

  1. CH3CH2NH2 + CH3COCl (with pyridine)
  2. Cyclohexanone + CH3NH2 (acid catalyst)
  3. (CH3)2NH + NaNO2/HCl
  4. CH3CH2CH2N(CH3)3+ HO−, heat
  1. N-Ethylacetamide, CH3CONHCH2CH3 (acylation); pyridine neutralizes the HCl.
  2. The N-methylimine of cyclohexanone and water.
  3. N-Nitrosodimethylamine, (CH3)2N–N=O.
  4. Propene, trimethylamine and water (Hofmann degradation).

2. Amide versus amine

Why is acetamide not basic, while ethylamine is?

In the amide the nitrogen lone pair is delocalized by resonance with the carbonyl (N–C=O ↔ N+=C–O−) and is not available to take up a proton. That is why acylation protects the amino group against acids, oxidants and electrophiles.

3. Tell the amines apart

How would you distinguish a primary, a secondary and a tertiary aliphatic amine with nitrous acid?

  1. The primary amine gives off N2 (the aliphatic diazonium salt decomposes) and gives alcohols, alkenes and other products.
  2. The secondary amine gives an N-nitrosoamine, an insoluble yellow oil.
  3. The tertiary amine shows no visible reaction: it forms a soluble N-nitrosoammonium salt.

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