34.3 Amides

2026 Syllabus Objectives

By the end of this topic, you should be able to:

  1. Recall how amides are made:
    • (a) Reaction between ammonia and an acyl chloride at room temperature
    • (b) Reaction between a primary amine and an acyl chloride at room temperature
  2. Describe the reactions of amides:
    • (a) Hydrolysis using aqueous alkali or aqueous acid
    • (b) Reduction of the C=O group in amides using LiAlH₄ to form an amine
  3. State and explain why amides are much weaker bases than amines

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What is an Amide?

An amide is an organic compound that contains the functional group –CONH₂ (or more broadly, –CO–NH–). This group is called the amide group or amide linkage.

  • The amide group contains a carbonyl group (C=O) directly bonded to a nitrogen atom (N).
  • A simple example is ethanamide, CH₃CONH₂, which is the amide made from ethanoic acid.

Think of an amide as a molecule that has both a C=O (like in acids and ketones) and a N–H (like in amines) joined together in one group.

Objective 1: How Are Amides Made?

Amides are made by reacting an acyl chloride with either ammonia or a primary amine.

What is an Acyl Chloride?

An acyl chloride is a reactive organic compound with the functional group –COCl. The simplest example is ethanoyl chloride, CH₃COCl. The –COCl group is very reactive because the chlorine atom is a good leaving group — it can be easily replaced by other atoms or groups.

(a) Reaction Between Ammonia and an Acyl Chloride

  • Reagents: Acyl chloride + Ammonia (NH₃)
  • Conditions: Room temperature — no heating needed because acyl chlorides are very reactive
  • What happens: The ammonia molecule attacks the acyl chloride. The –Cl is replaced by –NH₂, forming an amide. Hydrogen chloride (HCl) gas is also produced as a by-product.

Word equation:

Acyl chloride + Ammonia → Amide + Hydrogen chloride

Example using ethanoyl chloride:

CH₃COCl + 2NH₃ → CH₃CONH₂ + NH₄Cl

  • The first molecule of NH₃ reacts with the acyl chloride to form the amide (CH₃CONH₂) and release HCl gas.
  • The second molecule of NH₃ reacts with the HCl gas to form ammonium chloride (NH₄Cl), which is a white solid you might see as a cloud of fumes.

Key points to remember:

  • Conditions: room temperature
  • Product: an amide (–CONH₂)
  • By-product: HCl gas (which reacts with excess NH₃ to give NH₄Cl)

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