Question

Non-reducing sugars possess

• A. Free $-CHO$ group
• B. Free $-CO$ group
• C. Both A and B
• D. Neither A nor B

Answer 1

The correct option is D Neither A nor B

Non-reducing sugars have no free aldehyde or keto group so they are known as non- reducing sugar. The non-reducing sugar is not able to give a positive test for Fehling's test.

During Fehling's test when free aldehyde is present it is oxidized by bistartratocuprate (II) complex to a carboxylate anion and reduces the copper (II) ions of the complex to copper (I) ions. Red copper (I) oxide then precipitates and gives the positive test.

So, the correct answer is option D.