Pentan-1-ol (C₅H₁₁OH) is an alcohol. Describe how pentan-1-ol can be oxidised in the laboratory, name the organic product formed, and explain how you would confirm that oxidation has occurred.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Alcohols can be oxidised using an oxidising agent. The product of oxidising a primary alcohol is a carboxylic acid.
Model answer (5 marks)
1. Mix pentan‑1‑ol with acidified potassium dichromate(VI) (or acidified potassium manganate(VII)).
2. Heat the mixture, e.g. under reflux, until the reaction is complete.
3. The organic product is pentanoic acid.
4. Oxidation is confirmed by the colour change of the oxidising agent: orange dichromate turns green.
5. The product is identified as a carboxylic acid because it turns blue litmus paper red, has pH<7, and reacts with Na₂CO₃ to give CO₂ bubbles.
2. Heat the mixture, e.g. under reflux, until the reaction is complete.
3. The organic product is pentanoic acid.
4. Oxidation is confirmed by the colour change of the oxidising agent: orange dichromate turns green.
5. The product is identified as a carboxylic acid because it turns blue litmus paper red, has pH<7, and reacts with Na₂CO₃ to give CO₂ bubbles.
Examiner tips
- Use the exact oxidising agents and note the colour change; mention heating method; state the product name; give two confirmation tests (litmus and CO₂ evolution).
Common mistakes
- Mixing the oxidiser with the alcohol without acidification; forgetting to heat; confusing dichromate orange with green; not naming the product correctly.
Mark scheme (5 marks)
- Acidified potassium dichromate(VI) / acidified potassium manganate(VII) is used as the oxidising agent
- The mixture is heated (e.g. under reflux or warmed)
- The organic product formed is pentanoic acid
- The colour change of the oxidising agent confirms oxidation has occurred — acidified potassium dichromate(VI) changes from orange to green
- The product can be identified as a carboxylic acid because it turns blue litmus red / has a pH below 7 / reacts with sodium carbonate to produce bubbles of carbon dioxide
Key terms in this question
Related
- All Edexcel A-Level Chemistry (9CH0) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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