Question

Given below are two statements:
Statement I: Fructose does not contain an aldehydic group but still reduces Tollen’s reagent.
Statement II: In the presence of base, fructose undergoes rearrangement to give glucose.
In the light of the above statements, choose the correct answer from the options given below.

• A. Statement I is false but Statement II is true
• B. Both Statement I and Statement II are true
• C. Both Statement I and Statement II are false
• D. Statement I is true but Statement II is false

Hint:

Fructose is a ketose, but it has the ability to reduce Tollen's reagent due to the equilibrium with its aldose form. Always remember that sugar rearrangements can convert between different types of sugars, like ketoses to aldoses.

Answer 1

The Correct Option is B

Fructose is a ketohexose, meaning it contains a ketonic group, not an aldehydic group. However, in the presence of an alkaline medium, fructose can isomerize to form glucose and mannose via an enediol intermediate. This is known as the Lobry de Bruyn–Van Ekenstein transformation. Since glucose is an aldose sugar, it contains an aldehydic group that can reduce Tollen’s reagent (ammoniacal silver nitrate), resulting in the reduction of Tollen’s reagent. This explains Statement I, which is true because fructose does not directly contain an aldehydic group but can indirectly cause the reduction.

Statement II is also true because the isomerization of fructose in a basic medium as described above is well-established. 

Therefore, the correct answer is: Both Statement I and Statement II are true.