Chapter 11: Organic Chemistry — Part 7

Topic 11.7 · Carboxylic acids and esters

Formation and Reactions of Ethanoic Acid

Formation via Oxidation: Ethanol can be oxidised to ethanoic acid by heating it with acidified aqueous potassium manganate(VII) under reflux (colour changes from purple to colourless) or by bacterial oxidation when exposed to air.
Chemical Reactions: Ethanoic acid reacts like other acids:
- With Metals: Produces a metal ethanoate salt and hydrogen.
- With Bases: Undergoes neutralisation to form a salt and water.
- With Carbonates: Produces a salt, water, and carbon dioxide.

Exam Traps

Do not confuse oxidation of ethanol with fermentation — fermentation makes ethanol; manganate(VII) oxidation converts ethanol to ethanoic acid.
Do not forget reflux when heating with acidified manganate(VII) — without reflux, ethanol vaporises before it oxidises fully.

Esters are formed when a carboxylic acid reacts with an alcohol in the presence of an acid catalyst (e.g., sulfuric acid).

Functional Group: The ester linkage (-COO-).
General Equation: Carboxylic acid + Alcohol ? Ester + Water.
Naming: The alcohol provides the first part of the name (-yl) and the acid provides the second part (-oate).
Example: Ethanoic acid + Methanol ? Methyl ethanoate + Water.

Exam Traps

Do not reverse ester naming — methyl ethanoate comes from methanol + ethanoic acid, not ethanol + methanoic acid.
Do not confuse the ester functional group (−COO−) with the carboxyl group (−COOH) or hydroxyl group (−OH).

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