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*Revision Materials* 1 Atomic Structure 2 Atoms, molecules and stoichiometry 3 Chemical Bonding 4 States of matter 5 Chemical energetics 6 Electrochemistry 7 Equilibria 8 Reaction kinetics 9 The Periodic Table, chemical periodicity 10 Group 2 11 Group 17 12 Nitrogen and sulfur 13 Organic 14 Hydrocarbons 15 Halogen compounds 16 Hydroxy compounds 17 Carbonyl compounds 18 Carboxylic acids and derivatives 19 Nitrogen compounds 20 Polymerisation 21 Organic synthesis 22 Analytical techniques 23 Chemical energetics 24 Electrochemistry 25 Equilibria 26 Reaction kinetics 27 Group 2 28 Chemistry of transition elements 29 Organic 30 Hydrocarbons 31 Halogen compounds 32 Hydroxy compounds 33 Carboxylic acids and derivatives 34 Nitrogen compounds 35 Polymerisation 36 Organic synthesis 37 Analytical techniques

34 Nitrogen compounds

34.1 Primary and secondary amines 34.2 Phenylamine and azo compounds 34.3 Amides 34.4 Amino acids

Amides

Specification Reference Organic Chemistry, Nitrogen compounds 34.3

Quick Notes

  • Amide formation:
    • Ammonia + acyl chloride forms a primary amide
    • Primary amine + acyl chloride forms a secondary amide
  • Reactions of amides:
    • Hydrolysis:
      • Acid hydrolysis gives a carboxylic acid
      • Alkali hydrolysis gives a carboxylate salt
    • Reduction with LiAlH4 forms an amine
  • Basicity: Amides are much weaker bases than amines because their nitrogen lone pair is delocalised into the carbonyl group, reducing its ability to accept protons.

Full Notes

Preparation of Amide

Amides are derived from carboxylic acids where the –OH group is replaced with –NH2 (or a substituted amino group).

Amides can be formed from acyl chlorides with ammonia or amines.

Ammonia + Acyl Chloride → Primary Amide

CIE A-Level Chemistry reaction of acyl chloride with ammonia forming a primary amide.

Primary Amine + Acyl Chloride → Secondary Amide

CIE A-Level Chemistry reaction of acyl chloride with a primary amine forming a secondary amide.

In both cases, HCl is also produced which reacts with either the ammonia or amine, forming an ammonium chloride salt.

Hydrolysis of Amides

Amides can be hydrolysed back to carboxylic acids or carboxylate salts and amines/ammonia. The C–N bond in amides is relatively stable, so hydrolysis requires heating under reflux with acid or alkali.

With acid (e.g. dilute HCl, heat):

CIE A-Level Chemistry acid hydrolysis of amides forming a carboxylic acid and ammonium salt.

Example: CH3CONH2 + H2O + HCl → CH3COOH + NH4Cl

With alkali (e.g. NaOH, heat):

CIE A-Level Chemistry alkali hydrolysis of amides forming a carboxylate salt and ammonia.

Example:CH3CONH2 + NaOH → CH3COO−Na+ + NH3

Reduction of Amides

Amides can be reduced to amines by using lithium aluminium hydride (LiAlH4) in dry ether. This is a useful method for producing primary amines from amides.

CIE A-Level Chemistry reduction of amides with LiAlH4 forming a primary amine.

Example: CH3CONH2 + 4[H] → CH3CH2NH2 + H2O
(Ethanamide → ethylamine)

Basicity of Amides

Amides are much weaker bases than amines. In amides, the lone pair on the nitrogen is delocalised into the adjacent carbonyl group (C=O).

CIE A-Level Chemistry diagram showing delocalisation of the nitrogen lone pair in amides.

This explains why amides do not act as bases under normal conditions and do not react with acids the way amines do.

Summary