MCQ Detailed View

Lactic acid is an organic compound that has both a hydroxyl group (–OH) and a carboxyl group (–COOH) on adjacent carbon atoms. Its formula is CH₃–CH(OH)–COOH. When lactic acid reacts with alkaline potassium permanganate (KMnO₄ in basic medium), an oxidation reaction takes place. In this reaction, the hydroxyl group (–OH) of lactic acid is converted into a carbonyl group (C=O). Because of this change, lactic acid is transformed into pyruvic acid.

The structure of pyruvic acid is CH₃–CO–COOH. It is called an alpha-keto acid because it contains both a carboxyl group (–COOH) and a keto group (C=O) on the carbon next to it. This reaction does not remove any carbon atoms from the chain, it simply changes the hydroxyl group into a keto group.

Now let’s review the given options. Propionic acid is a simple three-carbon carboxylic acid, but it is not formed in this reaction because the hydroxyl group of lactic acid is oxidized, not removed. Cinnamic acid is an aromatic compound and completely unrelated to lactic acid. Tartaric acid is a dicarboxylic acid with two carboxyl groups, but it is also not related to this oxidation. Only pyruvic acid is the correct product because it matches the chemical change that happens during the oxidation of lactic acid.

This reaction is a good example of how oxidation can change a hydroxy acid into a keto acid. In biochemistry, pyruvic acid is very important because it is a key compound in energy production pathways such as glycolysis and the Krebs cycle. That means this reaction is not only important in organic chemistry but also has strong connections to biological systems.