Question

Assertion (A): All aliphatic aldehydes give a positive Fehling's test.
Reason (R): Aliphatic aldehydes are reduced by Fehling's reagent.

• A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Assertion (A) is false, but Reason (R) is true.

Hint:

Fehling’s Test: Aldehyde = reducing agent → oxidized to acid Cu\(^{2+}\) → Cu\(_2\)O (red precipitate)

Answer 1

The Correct Option is C

To solve this question, we need to evaluate the truth of both the assertion and the reason and determine their correctness in context.

1. Assertion (A): "All aliphatic aldehydes give a positive Fehling's test."
   • Fehling's test is a chemical test used to differentiate between water-soluble aldehyde and ketone functional groups and as a test for reducing sugars.
   • Aliphatic aldehydes generally give a positive Fehling's test because they are capable of reducing the copper(II) ions in Fehling's solution to copper(I) oxide, which precipitates as a red solid.
   • Therefore, the assertion is true.
2. Reason (R): "Aliphatic aldehydes are reduced by Fehling's reagent."
   • Fehling's reagent itself is not a reducing agent; rather, it is an oxidizing agent. The aldehydes are oxidized, and in the process, the copper(II) ions in the reagent are reduced to copper(I) oxide.
   • Therefore, the reason stated is incorrect because aliphatic aldehydes are oxidized by Fehling's reagent, not reduced.
3. Conclusion: Based on the above explanations, Assertion (A) is true, but Reason (R) is false. Therefore, the correct option is: Assertion (A) is true, but Reason (R) is false.