Butan-1-ol (C₄H₉OH) is an alcohol that can be oxidised. Explain how butan-1-ol can be oxidised in the laboratory, name the type of compound produced, and explain why vinegar contains a compound from the same type as the oxidation product of ethanol.

Edexcel A-Level Chemistry (9CH0) — 6.5 Alcohols and oxidation · Explain · 5 marks · View as Markdown

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

Alcohols can be oxidised both in the laboratory and by microorganisms. Ethanol is the alcohol found in alcoholic drinks. When wine is left open to the air, it turns sour over time.

Model answer (5 marks)

Butan‑1‑ol is oxidised in the laboratory by acidified potassium dichromate(VI) (or acidified potassium manganate(VII)). The mixture is heated or refluxed to drive the reaction. The oxidation stops at the carboxylic acid stage, giving butanoic acid. In wine, bacteria oxidise ethanol to ethanoic acid (acetic acid); this is also a carboxylic acid and is the compound that makes vinegar sour.

Examiner tips

  • Use the exact oxidising agents and state the reaction conditions (heat/reflux).
  • Mention the product as a carboxylic acid and give its name.
  • Explain the microbial oxidation of ethanol and link it to vinegar.

Mark scheme (5 marks)

  1. Acidified potassium dichromate(VI) (or acidified potassium manganate(VII)) is used as the oxidising agent
  2. The mixture is heated / refluxed to carry out the oxidation
  3. The product formed is a carboxylic acid (butanoic acid)
  4. Bacteria / microorganisms oxidise ethanol in wine (when exposed to air / oxygen)
  5. Ethanoic acid is produced, which is a carboxylic acid and is the compound that makes vinegar sour / acidic

Key terms in this question

oxidation

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