What does Benedict's test detect broadly?

What does Benedict's test detect broadly?

• A. Reducing sugars
• B. Amino acids
• C. Starches
• D. Proteins

Answer: (A)

Benedict's test detects reducing sugars, which are sugars that can donate electrons to the copper(II) ions in the reagent. In the alkaline, heated conditions of the test, these sugars reduce Cu2+ to Cu+, forming copper(I) oxide that appears as a brick-red precipitate. The presence of a free aldehyde group (in the open-chain form) or the ability of some ketoses to tautomerize to an aldose under these conditions explains why many common sugars (glucose, galactose, maltose, lactose) give positive results. This test does not generally detect starch, proteins, or amino acids, which lack the necessary reducing sugar functionality. Non-reducing sugars like sucrose won’t give a positive result unless they are hydrolyzed to producing reducing sugars.

Benedict's test detects reducing sugars, which are sugars that can donate electrons to the copper(II) ions in the reagent. In the alkaline, heated conditions of the test, these sugars reduce Cu2+ to Cu+, forming copper(I) oxide that appears as a brick-red precipitate. The presence of a free aldehyde group (in the open-chain form) or the ability of some ketoses to tautomerize to an aldose under these conditions explains why many common sugars (glucose, galactose, maltose, lactose) give positive results. This test does not generally detect starch, proteins, or amino acids, which lack the necessary reducing sugar functionality. Non-reducing sugars like sucrose won’t give a positive result unless they are hydrolyzed to producing reducing sugars.