Glucose acts as a reducing agent in Tollens' test because it contains which functional group?

• A. Carboxylic Group
• B. Hydroxyl Group
• C. Aldehyde Group
• D. Six Carbon Atoms

Answer: (C)

The aldehyde group enables the reducing action in Tollens' test. In solution, glucose exists in an open-chain form that has a terminal aldehyde. Under the alkaline conditions of Tollens' reagent, this aldehyde can be oxidized to a carboxylate, while silver ions are reduced to metallic silver, giving the familiar silver mirror. Other features, like hydroxyl groups, aren’t readily oxidized by this reagent, and simply having six carbon atoms isn’t a functional group that drives the reaction. So the key factor is the aldehyde group.