Methylamine (CH₃NH₂) is a simple amine that has a fishy smell and dissolves readily in water. Explain why methylamine is classified as an amine and describe the type of solution formed when methylamine dissolves in water, including why that type of solution is formed.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Methylamine (CH₃NH₂) is produced industrially and is used in the manufacture of pharmaceuticals. It has a strong, unpleasant fishy odour and dissolves readily in water.
Model answer (5 marks)
Methylamine contains a nitrogen atom bonded to a carbon atom, giving it the NH₂ functional group.
Amines are derived from ammonia – they have the same N–H bonds but one or more H atoms are replaced by alkyl or aryl groups.
When methylamine dissolves in water it reacts with water:
CH₃NH₂ + H₂O ⇌ CH₃NH₃⁺ + OH⁻
The lone pair on nitrogen accepts a proton from water, producing hydroxide ions.
Because hydroxide ions are formed, the solution is alkaline (basic).
Amines are derived from ammonia – they have the same N–H bonds but one or more H atoms are replaced by alkyl or aryl groups.
When methylamine dissolves in water it reacts with water:
CH₃NH₂ + H₂O ⇌ CH₃NH₃⁺ + OH⁻
The lone pair on nitrogen accepts a proton from water, producing hydroxide ions.
Because hydroxide ions are formed, the solution is alkaline (basic).
Examiner tips
- Use the term ‘amine’ to refer to the NH₂ group attached to a carbon; link to ammonia structure.
- Show the proton‑accepting reaction with water and the resulting OH⁻ ions.
- Explain that the presence of OH⁻ makes the solution basic.
- Use correct UK spelling (e.g. ‘alkaline’).
Common mistakes
- Calling the solution acidic instead of alkaline.
- Forgetting to mention the proton‑accepting reaction or the formation of OH⁻.
- Using the wrong functional‑group description (e.g. ‘amine group’ without noting the N–C bond).
Mark scheme (5 marks)
- Methylamine contains a nitrogen atom / NH₂ group bonded to a carbon atom / hydrocarbon group
- Amines are derived from ammonia / are related to ammonia in structure
- The solution formed is alkaline / basic
- Methylamine / the amine accepts a proton from water OR donates a lone pair of electrons to a proton / reacts with water to produce hydroxide ions (OH⁻)
- Amines are bases (like ammonia) / the nitrogen lone pair makes amines basic
Key terms in this question
Related
- All Eduqas A-Level Chemistry revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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