Lactic acid on oxidation by alkaline potassium permanganate gives:____________?
Correct answer: C. Pyruvic acid
- A. Propionic acid
- B. Cinnamic acid
- C. Pyruvic acid
- D. Tartaric acid
Explanation
Lactic acid, CH3CH(OH)COOH, contains a secondary alcohol group that alkaline potassium permanganate oxidizes to a ketone, giving CH3COCOOH, pyruvic acid. The carboxylic acid group remains unchanged under this oxidation. The likely wrong choice is propionic acid because it has a similar three-carbon skeleton, but oxidation changes the alcohol group rather than removing the oxygen-containing functionality.
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About Reactivity of Carboxylic Acids
Carboxylic acids show acidic behaviour because their carboxylate ions are resonance-stabilised, and electron-withdrawing groups can change their strength. Reactions include neutralisation, esterification, formation of acid chlorides and amides, reduction, decarboxylation and substitution at the acyl carbon, which differs from the reactions of phenols.
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