Question

Which one of the following does NOT form a silver mirror on heating with Tollen’s reagent?

Options

• Glucose

• Fructose

• Sucrose

• Lactose

Answer 1

Sucrose

Explanation:

Tollen’s reagent is utilized to identify reducing sugars, which possess a free aldehyde (-CHO) or ketone (-CO) group that can reduce Ag⁺ ions to metallic silver, resulting in the formation of a silver mirror. Among the provided possibilities, sucrose (C₁₂H₂₂O₁₁) is classified as a non-reducing sugar due to its composition as a disaccharide formed from glucose and fructose, which are interconnected by a glycosidic bond at the anomeric carbons (C₁ of glucose and C₂ of fructose). This connection inhibits the exposure of the free aldehyde (-CHO) or ketone (-C=O) group. Due to the absence of a free hemiacetal or aldehyde group, sucrose is incapable of reducing Tollen’s reagent. Consequently, sucrose does not produce a silver mirror in Tollen’s test.