Prepare an N-substituted amide from a primary amine and an acyl chloride
A primary amine reacts with an acyl chloride at room temperature to form an N-substituted amide.
Section 34 · Nitrogen compounds
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
What happens to the carbon group attached to a primary amine during acylation?
What you will learn
- Recall primary amines as amide-forming nucleophiles
- Preserve the amine substituent on nitrogen
- State room temperature and HCl formation
Retain the amine's carbon group
A primary amine reacts with an acyl chloride at room temperature to form an amide. For R′NH₂, the product is RCONHR′: the amine's R′ group remains attached to nitrogen.
For example, ethanoyl chloride plus methylamine gives N-methylethanamide and HCl. Excess amine may accept the HCl and form an ammonium salt.
Distinguish primary from secondary products
A primary amine initially has one carbon group and two hydrogens on N. After acylation, the amide nitrogen has one carbon group from the amine, one acyl group and one H.
The product is an amide because its nitrogen is directly bonded to a carbonyl carbon. Keep the reaction at room temperature as specified.
Pause and explain
What product class forms from a primary amine and an acyl chloride?
Worked example
Predict the product from ethanoyl chloride and ethylamine.
Show the worked solution
- Keep the ethanoyl carbonyl.
- Attach the amine nitrogen to the acyl carbon.
- Retain the ethyl group on nitrogen.
Answer N-ethylethanamide, CH₃CONHCH₂CH₃, and HCl.
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Test this topic →From guided practice to a new situation
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.
Complete CH₃CH₂COCl + CH₃NH₂ → …
Give me a hint
Replace chlorine with NHCH₃.
Compare my reasoning
- Retain the propanoyl fragment.
- Keep methyl on nitrogen.
- Include HCl.
CH₃CH₂CONHCH₃ + HCl (N-methylpropanamide and hydrogen chloride).
Look for these in your work
- Acyl group
- N-methyl group
- HCl
Explain why the product from propanoyl chloride and methylamine is not propanamide.
Give me a hint
Compare the nitrogen substituents.
Compare my reasoning
- Methylamine contributes a methyl group to nitrogen.
- The product nitrogen therefore has one N–H bond.
- Name the product N-methylpropanamide.
The methyl group from methylamine remains on nitrogen, so the product is N-methylpropanamide rather than propanamide.
Look for these in your work
- Substituent retained
- N–H count
- Name
A response predicts methyl propanoate from propanoyl chloride and methylamine. Identify the mistaken nucleophile assumption.
Give me a hint
An amine contributes nitrogen, not an alcohol oxygen.
Compare my reasoning
- Methylamine contains nitrogen.
- It forms a C(O)–N amide bond.
- Methyl propanoate would require methanol.
The product is N-methylpropanamide; an ester would require an alcohol such as methanol.
Look for these in your work
- Reagent atom
- Amide bond
- Ester distinction
Common mistakes
- Dropping the ethyl substituent from nitrogen
- Calling the product an amine
- Writing an ester
- Using heat as the specified condition
What can you explain now?
What happens to the carbon group attached to a primary amine during acylation?
Compare with the explanation
It remains attached to nitrogen
The product is N-substituted.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
How does the primary amine's substituent appear in the amide product?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.