Methanol and ethanol are both alcohols. Explain why both of these substances are classified as alcohols and describe two chemical reactions that alcohols undergo.

WJEC A-Level Chemistry (Wales) — 4.3 Alcohols and phenols · Explain and Describe · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (5 marks)

Both methanol and ethanol contain a hydroxyl (-OH) functional group, which defines them as alcohols.

1. They burn in oxygen/air to give CO₂ and H₂O.
2. They react with sodium metal to give NaOCH₃ (or NaOCH₂CH₃) and H₂ gas.
3. They can be oxidised; for example, ethanol → ethanoic acid.
4. They react with carboxylic acids (acid‑catalysed) to give esters (e.g. CH₃CH₂OH + CH₃COOH → CH₃COOCH₂CH₃ + H₂O).

Examiner tips

  • Use the keyword ‘contain’ to link the –OH group to the definition of alcohols. Show each reaction with a clear balanced equation. Mention the role of an acid catalyst in esterification.
  • Include the products (CO₂, H₂O, H₂, acid, ester) to demonstrate full understanding.

Common mistakes

  • Forgetting to mention the –OH group as the defining feature. Not balancing the equations or omitting the acid catalyst in esterification. Confusing alcohols with other oxygen‑containing compounds such as ethers.

Mark scheme (5 marks)

  1. Both contain a hydroxyl (-OH) functional group
  2. Alcohols burn/combust in oxygen/air to produce carbon dioxide and water
  3. Alcohols react with sodium to produce hydrogen gas
  4. Alcohols can be oxidised to form carboxylic acids (e.g. ethanol oxidised to ethanoic acid)
  5. Alcohols react with carboxylic acids (in the presence of an acid catalyst) to form esters

Key terms in this question

alcohol

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