Explain why amides are much weaker bases than amines
An amide nitrogen lone pair is delocalised toward the carbonyl, making it much less available to accept a proton than an amine lone pair.
A Level; Cambridge International Chemistry 9701, 2028–2030 syllabus, Topic 34. Use the stated reagents, conditions and product scope. Written practice is self-checked This online lesson cannot demonstrate supervised laboratory skills.
Before you begin
- Recall nucleophilic substitution, reduction, acyl-chloride addition–elimination, acid–base equilibria and covalent bonding.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Why is an amide nitrogen less basic than an amine nitrogen?
What you will learn
- Compare amide and amine basicity
- Explain lone-pair delocalisation
- Connect availability of the lone pair to proton acceptance
The carbonyl draws nitrogen's lone pair into resonance
In an amide, nitrogen is directly attached to a carbonyl carbon. Its lone pair overlaps with the C=O system and is delocalised, giving the C–N bond partial double-bond character.
Because that lone pair is less available to bond to H⁺, an amide is much weaker as a base than a comparable amine.
Compare with an amine
In an amine, the nitrogen lone pair is more localised and can accept H⁺ more readily.
Do not say that an amide has no lone pair. The key point is that delocalisation reduces its availability; it does not remove the electron pair from the molecule.
Pause and explain
What bond feature is consistent with amide lone-pair delocalisation?
Worked example
Explain why ethanamide is a much weaker base than ethylamine.
Show the worked solution
- Both contain nitrogen with a lone pair.
- In ethanamide, the lone pair delocalises toward C=O.
- In ethylamine, the lone pair is more available to accept H⁺.
Answer Ethanamide is much less basic because its nitrogen lone pair is delocalised into the carbonyl and is less available to accept a proton.
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Compare the nitrogen lone pair in ethanamide and ethylamine.
Give me a hint
Use the neighbouring carbonyl group.
Compare my reasoning
- Ethanamide N is attached to C=O.
- Its lone pair delocalises into the carbonyl system.
- Ethylamine's lone pair is more localised and available.
The amide lone pair is delocalised toward C=O; the amine lone pair is more available to accept H⁺.
Look for these in your work
- Functional groups
- Delocalisation
- Basicity linked
Explain the partial double-bond character of an amide C–N bond.
Give me a hint
Describe resonance involving the nitrogen lone pair.
Compare my reasoning
- Nitrogen's lone pair overlaps with the carbonyl π system.
- Electron density is delocalised across C–N and C=O.
- The C–N bond gains partial double-bond character.
The N lone pair is delocalised into the carbonyl, so the C–N bond has partial double-bond character.
Look for these in your work
- Lone pair
- Carbonyl interaction
- Bond character
A student writes ‘amides are weak bases because the nitrogen is sp³ and has no lone pair’. Correct the explanation.
Give me a hint
Keep the lone pair and explain its availability.
Compare my reasoning
- Amide nitrogen does have a lone pair.
- It is delocalised toward the carbonyl.
- This makes proton acceptance much less favourable than for amines.
Amide nitrogen has a lone pair, but the pair is delocalised into C=O and is less available to accept H⁺; amides are much weaker bases than amines.
Look for these in your work
- Lone pair retained
- Delocalisation
- Basicity explanation
Common mistakes
- Claiming amide nitrogen has no lone pair
- Saying the lone pair is delocalised toward the alkyl chain
- Ignoring the carbonyl group
- Calling amides stronger bases than amines
What can you explain now?
Why is an amide nitrogen less basic than an amine nitrogen?
Compare with the explanation
Its lone pair is delocalised toward the carbonyl
Delocalisation reduces availability to accept H⁺.
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Make it stick
How does carbonyl resonance reduce the basicity of an amide nitrogen?
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