Ethanol can be converted to ethene, or it can be converted to ethanoic acid. (i) State the reagent and condition used for each conversion. (ii) One conversion is a dehydration and the other is an oxidation — explain what each term means in the context of these specific reactions. (iii) Why is the product of oxidation classified as belonging to a different homologous series than ethanol?
Generated by claude-sonnet-4-6 · 2026-06-26 01:12 · grounding rag
Model Answer
(i) Reagents and Conditions:
- Ethanol → Ethene (dehydration): Reagent — excess concentrated H₂SO₄; Condition — heated at 443 K.
- Ethanol → Ethanoic acid (oxidation): Reagent — alkaline KMnO₄ or acidified K₂Cr₂O₇ (oxidising agent); Condition — heated.
(ii) Meaning of each term:
- Dehydration means removal of water from a molecule. Here, conc. H₂SO₄ removes H and OH from ethanol to form ethene (CH₂=CH₂) and H₂O.
- Oxidation means addition of oxygen (or removal of hydrogen). Here, an oxidising agent adds oxygen to ethanol (–OH group) to form ethanoic acid (–COOH), increasing the oxygen content.
(iii) Different homologous series:
Ethanol belongs to the alcohol series (functional group: –OH), while ethanoic acid belongs to the carboxylic acid series (functional group: –COOH). A homologous series is defined by its functional group, and since the two compounds have different functional groups with different chemical properties, they belong to different homologous series.
Source: Chapter 4, Section 4.4.1 (Properties of Ethanol); Section 4.2.4 (Homologous Series)
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Explanation
- For (i), the textbook explicitly states conc. H₂SO₄ at 443 K for dehydration. For oxidation, the textbook question asks why it is oxidation — oxidising agents like KMnO₄/K₂Cr₂O₇ are the standard expected reagents; mention either.
- For (ii), examiners want the general definition applied to these reactions specifically — don't just define in the abstract.
- For (iii), the key concept is from Section 4.2.4: a homologous series is identified by its functional group. Two compounds with different functional groups (–OH vs –COOH) cannot belong to the same series, regardless of carbon chain length. State both functional groups clearly for full marks.