Methylamine is a simple amine with the molecular formula CH₃NH₂. Explain why methylamine is classified as an amine and describe two properties that methylamine shares with ammonia, giving a reason for each property.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Methylamine (CH₃NH₂) is a gas at room temperature that dissolves readily in water to form an alkaline solution. It is produced naturally during the decomposition of some proteins.
Model answer (5 marks)
Methylamine is classified as an amine because it contains a nitrogen atom bonded to a carbon atom – the NH₂ group is attached to a hydrocarbon group.
Property 1: Methylamine dissolves in water to give an alkaline solution, just like ammonia.
Reason: Both methylamine and ammonia are bases; they accept a proton from water, forming NH₃⁺ (or CH₃NH₃⁺) and OH⁻ ions.
Property 2: Methylamine has a characteristic pungent, fishy smell, similar to ammonia.
Reason: Both compounds contain a lone pair of electrons on nitrogen and are small, volatile molecules with similar functional groups, giving rise to comparable intermolecular interactions and odour.
Property 1: Methylamine dissolves in water to give an alkaline solution, just like ammonia.
Reason: Both methylamine and ammonia are bases; they accept a proton from water, forming NH₃⁺ (or CH₃NH₃⁺) and OH⁻ ions.
Property 2: Methylamine has a characteristic pungent, fishy smell, similar to ammonia.
Reason: Both compounds contain a lone pair of electrons on nitrogen and are small, volatile molecules with similar functional groups, giving rise to comparable intermolecular interactions and odour.
Examiner tips
- Use the exact phrase ‘contains a nitrogen atom bonded to a carbon atom’ for the classification point.
- Show the base reaction for both compounds to justify the alkaline solution property.
- Mention the lone pair on nitrogen to explain the similar smell.
- Keep the answer concise – no extra sentences.
Mark scheme (5 marks)
- Methylamine is classified as an amine because it contains a nitrogen atom / NH₂ group bonded to a carbon atom / hydrocarbon group
- Property 1: methylamine dissolves in water to form an alkaline solution (like ammonia)
- Reason for property 1: both methylamine and ammonia accept a proton from water / act as bases / produce OH⁻ ions in solution
- Property 2: methylamine has a characteristic / pungent / fishy smell (like ammonia)
- Reason for property 2: both methylamine and ammonia have a lone pair of electrons on nitrogen / similar nitrogen-containing structure, leading to similar intermolecular interactions / volatile small molecules with similar functional groups
Key terms in this question
Related
- All WJEC A-Level Chemistry (Wales) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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