Amides
| English | Chinese | Pinyin |
|---|---|---|
| amide | 酰胺 | xiān àn |
| hydrolysed | 水解 | shuǐ jiě |
| delocalised | 离域 | lí yù |
| peptide bond | 肽键 | tài jiàn |
| polyamide | 聚酰胺 | jù xiān àn |
The amide 酰胺 link
- An amide is made from ammonia (or an amine) and an acyl chloride.
- It can be hydrolysed 水解 back apart, or reduced to an amine.
- It is a much weaker base than an amine — and that has a neat explanation.
Amide formation route
Follow acyl chloride or acid derivative to an amide.
An amide is made from an acyl chloride and:
Ammonia or a 1°/2° amine reacts with an acyl chloride to give an amide.
The functional group –CONH₂ is found in an ______.
Formed from an acyl chloride and ammonia or an amine.
Making and reactions
- Make it: ammonia or a primary amine + an acyl chloride (room temperature).
- Hydrolysis (aqueous acid or alkali) → the carboxylic acid (or its salt) + the amine (or ammonium).
- Reduction of the C=O with $\text{LiAlH}_4$ → an amine.
Hydrolysing ethanamide (CH₃CONH₂):
- with acid: → ethanoic acid (CH₃COOH) + an ammonium salt.
- with alkali (NaOH): → sodium ethanoate (CH₃COO⁻Na⁺) + ammonia.
Same split of the C–N bond; the products just depend on whether acid or base is present.
Paracetamol contains the amide group (-CONH-).
Hydrolysing an amide gives:
Acid or alkali hydrolysis splits the amide into the carboxylic acid and the amine.
Reducing an amide with LiAlH₄ gives:
LiAlH₄ reduces the amide C=O to give an amine.
Match each term to its meaning.
Each item links the term to its correct meaning.
Weakly basic
- An amide is a much weaker base than an amine.
- Its nitrogen lone pair is delocalised 离域 onto the neighbouring C=O group, so it is not available to accept $\text{H}^+$.
- That same delocalisation makes the amide link flat and unusually stable.
An amide is a much weaker base than an amine because its nitrogen lone pair is:
Delocalisation onto the adjacent carbonyl makes the lone pair unavailable, so the amide is barely basic.
The amide link in nature and materials
- The –CONH– link is the peptide bond 肽键 that joins amino acids into proteins.
- The very same link joins monomers in nylon and other polyamides 聚酰胺.
- Its stability is why proteins and nylon hold together so well.
You've got it
- an amide forms from ammonia/amine + acyl chloride
- it hydrolyses to a carboxylic acid/salt (+ amine), and reduces ($\text{LiAlH}_4$) to an amine
- it is a much weaker base than an amine (lone pair delocalised onto the C=O)
- the –CONH– link is the peptide bond in proteins and the link in nylon