Prepare a primary amide from ammonia and an acyl chloride
Ammonia reacts with an acyl chloride at room temperature to form a primary amide and HCl.
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 amide class forms from ammonia and an acyl chloride?
What you will learn
- Recall ammonia and an acyl chloride as reactants
- State room temperature
- Identify the primary amide product
Replace chlorine with NH₂
An acyl chloride reacts with ammonia at room temperature to form a primary amide. The nitrogen atom bonds to the acyl carbon, replacing chlorine.
At the organic-product level, RCOCl + NH₃ → RCONH₂ + HCl. If excess ammonia is shown in a balanced preparation equation, a second NH₃ molecule can neutralise HCl to form NH₄Cl.
Identify a primary amide
The product RCONH₂ has a carbonyl group directly bonded to nitrogen. It is a primary amide because nitrogen retains two hydrogens.
Keep the acyl carbonyl and the carbon skeleton. Do not confuse the amide with an amine, which lacks the adjacent carbonyl group.
Pause and explain
What condition is specified for amide formation from ammonia and an acyl chloride?
Worked example
Predict the organic product from propanoyl chloride and ammonia at room temperature.
Show the worked solution
- Keep the propanoyl skeleton.
- Replace Cl with NH₂.
- Classify the product by its C(O)NH₂ group.
Answer Propanamide, CH₃CH₂CONH₂, forms with HCl.
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Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
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 CH₃COCl + NH₃ → … at the organic-product level.
Give me a hint
Replace acyl chlorine with NH₂.
Compare my reasoning
- Retain the ethanoyl carbonyl.
- Form CH₃CONH₂.
- Write HCl as the by-product.
CH₃CONH₂ + HCl (ethanamide and hydrogen chloride).
Look for these in your work
- Carbonyl retained
- Primary amide
- HCl
Classify CH₃CH₂CONH₂ and explain the class name.
Give me a hint
Count carbon groups directly bonded to the amide nitrogen.
Compare my reasoning
- The nitrogen is attached to one acyl carbon.
- It retains two hydrogens.
- This is a primary amide.
Propanamide is a primary amide because its –CONH₂ nitrogen has two hydrogens.
Look for these in your work
- Amide group
- N–H count
- Class
A learner labels CH₃CONH₂ ‘ethylamine’. Correct the structure-based name.
Give me a hint
The carbonyl carbon is attached directly to nitrogen.
Compare my reasoning
- The structure contains C=O next to N.
- That is an amide linkage.
- The correct compound is ethanamide.
CH₃CONH₂ is ethanamide, a primary amide, not ethylamine.
Look for these in your work
- Carbonyl noticed
- Amide class
- Name corrected
Common mistakes
- Writing propylamine
- Removing the carbonyl oxygen
- Using an alcohol to make an amide
- Omitting room temperature
What can you explain now?
What amide class forms from ammonia and an acyl chloride?
Compare with the explanation
A primary amide
The product contains –CONH₂.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
How does ammonia replace chlorine in an acyl chloride to form a primary amide?
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.