React an acyl chloride with ammonia to form an amide
Ammonia reacts with an acyl chloride at room temperature to form a primary amide, with excess ammonia accepting the HCl.
Section 33 · Carboxylic acids and derivatives
A Level; Cambridge International Chemistry 9701, 2028–2030 syllabus, Topic 33. Focus on the named compounds, reagents and conditions in each outcome; apply the specified reaction type rather than extending it to unlisted cases. Written practice is self-checked
Before you begin
- Recall carboxylic acids, esters, phenols, alcohols, halogenoalkanes and electrophilic/nucleophilic reaction ideas from earlier topics.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What organic product forms from an acyl chloride and ammonia?
What you will learn
- Recall amide formation from ammonia and an acyl chloride
- Identify a primary amide product
- Account for HCl and ammonium salt when balancing with excess ammonia
Ammonia replaces the acyl chlorine
Ammonia reacts with an acyl chloride at room temperature to form a primary amide. The nucleophilic nitrogen bonds to the acyl carbon, replacing chlorine.
At the organic-product level, write RCOCl + 2NH₃ → RCONH₂ + NH₄Cl. One NH₃ forms the amide; another accepts the HCl formed during substitution. The syllabus describes the products as an amide and HCl.
Check the amide type
The product RCONH₂ is a primary amide because the nitrogen is bonded to one acyl group and two hydrogens.
Do not put two nitrogen atoms into the amide. Excess ammonia also neutralises HCl, so ammonium chloride is the balanced salt when the base is shown explicitly.
Pause and explain
Why can NH₄Cl appear in the balanced equation when excess ammonia is used?
Worked example
Predict the organic product from propanoyl chloride and ammonia.
Show the worked solution
- Replace Cl at the acyl carbon with NH₂.
- Keep the propanoyl carbon skeleton.
- Recognise a primary amide.
Answer Propanamide, CH₃CH₂CONH₂, forms; excess NH₃ gives NH₄Cl from the 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 the balanced reaction of ethanoyl chloride with excess ammonia.
Give me a hint
One ammonia provides the amide nitrogen; another neutralises HCl.
Compare my reasoning
- Form CH₃CONH₂.
- The substitution generates HCl.
- Use a second NH₃ to form NH₄Cl.
CH₃COCl + 2NH₃ → CH₃CONH₂ + NH₄Cl.
Look for these in your work
- Primary amide
- Two ammonia molecules
- Salt balanced
Classify CH₃CH₂CONH₂ and explain the nitrogen substitution.
Give me a hint
Count carbon groups bonded to the amide nitrogen.
Compare my reasoning
- The nitrogen is attached to one carbonyl carbon.
- It retains two hydrogens.
- This is a primary amide.
CH₃CH₂CONH₂ is propanamide, a primary amide with –CONH₂.
Look for these in your work
- Acyl skeleton
- Nitrogen substituents
- Amide class
A student writes CH₃COCl + NH₃ → CH₃CH₂NH₂ + HCl. Identify the changes that do not belong to this reaction.
Give me a hint
Track the carbon skeleton and keep the carbonyl carbon.
Compare my reasoning
- The reaction substitutes at the acyl carbon.
- The carbonyl remains in the amide.
- The product is CH₃CONH₂, not an amine with a longer chain.
Ethanoyl chloride forms ethanamide, CH₃CONH₂, not ethylamine; the carbonyl carbon stays in the molecule.
Look for these in your work
- Carbon count
- Carbonyl retained
- Product class
Common mistakes
- Writing an amine instead of an amide
- Leaving Cl attached to the carbonyl carbon
- Ignoring HCl neutralisation when balancing with excess NH₃
- Using heat rather than room temperature
What can you explain now?
What organic product forms from an acyl chloride and ammonia?
Compare with the explanation
A primary amide
The product has the group RCONH₂.
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Make it stick
What amide forms from an acyl chloride and ammonia, and how is HCl handled?
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.