Ethanol is treated separately with (i) alkaline potassium permanganate and (ii) excess concentrated sulphuric acid at 443 K. In each case, identify the organic product formed and explain why the two reactions belong to different categories of chemical reactions.
Generated by claude-sonnet-4-6 · 2026-06-26 01:10 · grounding rag
Model Answer
(i) When ethanol is treated with alkaline potassium permanganate, it is oxidised to form ethanoic acid (CH₃COOH).
(ii) When ethanol is heated with excess concentrated sulphuric acid at 443 K, dehydration occurs and ethene (CH₂=CH₂) is formed along with water.
Different categories:
- Reaction (i) is an oxidation reaction — oxygen is added to ethanol by the oxidising agent (alkaline KMnO₄).
- Reaction (ii) is a dehydration (elimination) reaction — water is removed from ethanol by the dehydrating agent (conc. H₂SO₄), producing an unsaturated hydrocarbon.
Thus, one reaction involves addition of oxygen, while the other involves removal of water — making them fundamentally different types.
Source: Chapter 4, Sections 4.3.2 and 4.4.1
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Explanation
- Examiners expect both products named correctly — ethanoic acid and ethene — for full credit.
- You must clearly contrast the two reaction types: oxidation vs dehydration/elimination. Just naming the products is not enough.
- Use key terms: oxidising agent, dehydrating agent, oxygen added, water removed.
- The 3-mark split is typically: 1 mark for each product + 1 mark for explaining the two different categories.