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

To address the question, each statement is evaluated independently using established chemical principles.

Statement I: Fructose lacks an aldehydic group but reduces Tollen’s reagent.

Explanation: Fructose is classified as a ketohexose, possessing a ketone group instead of an aldehyde. While Tollen's reagent typically detects aldehydes, fructose reduces it due to its ability to isomerize under basic conditions (present in Tollen's test). This isomerization, via enediol rearrangement, yields glucose and mannose, which do possess aldehyde groups and consequently reduce the reagent.

Consequently, Statement I is verified as true.

Statement II: Fructose rearranges to glucose in a basic environment.

Explanation: Under basic conditions, fructose undergoes isomerization, known as the Lobry de Bruyn–Van Ekenstein transformation. This reaction forms enediol intermediates, facilitating the conversion of fructose into glucose and mannose. This process confirms fructose's indirect reduction of Tollen's reagent by forming an aldehyde group.

Therefore, Statement II is validated as true.

The chemical basis for both statements is confirmed, establishing their truthfulness.

Conclusion: The accurate response is that both Statement I and Statement II are true.