Prepare a primary amine from a halogenoalkane
Recall the substitution route that uses ammonia in ethanol, heat and pressure to form an amine.
AS Level; Cambridge International Chemistry 9701, syllabus for 2028–2030. Classification of amines is not tested at AS Level. Cyanides, hydrogen cyanide and pressurised reactions are hazardous: these examples teach exam chemistry, not practical instructions. Written practice is self-checked
Before you begin
- Use nucleophilic substitution and addition, carbonyl compounds, functional-group names and balanced equations from Topics 13–18.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which reagent supplies the nitrogen in this preparation?
What you will learn
- Name ammonia and ethanol as the reagent and solvent
- State heating under pressure
- Represent the substitution and balance the overall equation
Replace the halogen with an amino group
A halogenoalkane reacts with NH₃ in ethanol when heated under pressure. A carbon–halogen bond is replaced by a carbon–nitrogen bond, producing a primary amine. This is nucleophilic substitution: the nitrogen lone pair forms a bond to the carbon while the halide leaves.
For bromoethane, the organic product is ethanamine, CH₃CH₂NH₂. An overall equation with excess ammonia can be written CH₃CH₂Br + 2NH₃ → CH₃CH₂NH₂ + NH₄Br. Keep the organic product and the ammonium halide by-product distinct.
Keep the stated conditions together
Recall the full combination: ammonia, ethanol, heat and pressure. Pressure allows the reaction to be carried out with ammonia in the reaction mixture; do not replace the solvent with aqueous ammonia or omit the pressure condition.
At AS, the syllabus specifically says classification of amines is not tested. Learn this preparation and identify the primary-amine product, but do not spend this pathway on classifying secondary or tertiary amines.
Pause and explain
Which condition completes the stated AS preparation of an amine?
Worked example
State the reagents and conditions to prepare ethanamine from bromoethane.
Show the worked solution
- Use ammonia as the nucleophile.
- Use ethanol as the solvent.
- Heat under pressure; replace Br with NH₂.
Answer React bromoethane with NH₃ in ethanol, heating under pressure, to form ethanamine.
Try a topic test
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.
Prepare propan-1-amine from 1-bromopropane. Give the reagent, solvent and conditions.
Give me a hint
Keep the carbon skeleton and replace Br by NH₂.
Compare my reasoning
- Use NH₃ in ethanol.
- Heat under pressure.
- The organic product retains three carbons.
1-bromopropane + NH₃ in ethanol, heated under pressure, forms propan-1-amine.
Look for these in your work
- Ammonia named
- Ethanol and pressure/heat included
- Three-carbon amine identified
Complete the organic product: CH₃CH₂CH₂Br → ? using NH₃ in ethanol under pressure.
Give me a hint
Only the halogen substituent is replaced in the product skeleton.
Compare my reasoning
- Keep the three-carbon chain.
- Replace Br with NH₂.
- Name the terminal amine using the retained chain.
CH₃CH₂CH₂NH₂, propan-1-amine.
Look for these in your work
- Carbon count retained
- Correct group replacement
- Product name matches structure
A student lists aqueous NH₃ at room temperature to convert a halogenoalkane to an amine. Correct the answer and explain the key change.
Give me a hint
Recall the full combination of solvent and conditions from the syllabus.
Compare my reasoning
- Use ammonia in ethanol.
- Include heating under pressure.
- Identify the reaction as substitution.
Use NH₃ in ethanol, heated under pressure; the halogen is substituted by an amino group.
Look for these in your work
- Solvent corrected
- Pressure and heat stated
- Substitution described
Common mistakes
- Using aqueous ammonia instead of NH₃ in ethanol
- Forgetting heat or pressure
- Calling the product an amide
- Treating amine classification as an AS requirement
What can you explain now?
Which reagent supplies the nitrogen in this preparation?
Compare with the explanation
NH₃
Ammonia is the nucleophile that replaces the halogen.
After trying it yourself, choose your next review. This is your self-assessment.
Your review choice appears on Today. Sign in to sync it across devices.
Make it stick
Which reagent, solvent and conditions are required to prepare an amine from a halogenoalkane?
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.