Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : Ketoses give Seliwanoff's test faster than Aldoses. Reason (R) : Ketoses undergo \beta -elimination followed by formation of furfural. In the light of the above statements, choose the correct answer from the options given below :

Both (A) and (R) are true but (R) is not the correct explanation of (A)

Both (A) and (R) are true and (R) is the correct explanation of (A)

Biomolecules PYQ — JEE Main 2023 · 30 Jan · Shift 1 · Q4 with Solution

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Correct answer: C

Understand Seliwanoff’s test

Seliwanoff’s test distinguishes ketoses from aldoses.
- In concentrated acid, ketoses dehydrate more rapidly than aldoses.
- They form hydroxymethylfurfural quickly, which then reacts with resorcinol to give a cherry-red color.
- Aldoses also may respond, but much more slowly.
Therefore, the assertion

$\text{Ketoses give Seliwanoff's test faster than aldoses}$

is true.
Examine the reason

The reason says:

$\text{Ketoses undergo } \beta\text{-elimination followed by formation of furfural.}$

This is not the correct description of Seliwanoff’s test.

In reality:
- Ketoses undergo acid-catalyzed dehydration more readily.
- Hexoses form 5-hydroxymethylfurfural, not simply furfural.
- The statement involving $\beta$ -elimination is not the accepted explanation here.
Hence, the reason is false.
Match with the options
- A: Assertion false, Reason true $\rightarrow$ incorrect
- B: Both true, but Reason not explanation $\rightarrow$ incorrect
- C: Assertion true, Reason false $\rightarrow$ correct
- D: Both true, and Reason correct explanation $\rightarrow$ incorrect
Final conclusion

The correct option is:

$\boxed{\text{C}}$

View written solutionFree

Correct answer: C

Understand Seliwanoff’s test

Seliwanoff’s test distinguishes ketoses from aldoses.
- In concentrated acid, ketoses dehydrate more rapidly than aldoses.
- They form hydroxymethylfurfural quickly, which then reacts with resorcinol to give a cherry-red color.
- Aldoses also may respond, but much more slowly.
Therefore, the assertion

$\text{Ketoses give Seliwanoff's test faster than aldoses}$

is true.
Examine the reason

The reason says:

$\text{Ketoses undergo } \beta\text{-elimination followed by formation of furfural.}$

This is not the correct description of Seliwanoff’s test.

In reality:
- Ketoses undergo acid-catalyzed dehydration more readily.
- Hexoses form 5-hydroxymethylfurfural, not simply furfural.
- The statement involving $\beta$ -elimination is not the accepted explanation here.
Hence, the reason is false.
Match with the options
- A: Assertion false, Reason true $\rightarrow$ incorrect
- B: Both true, but Reason not explanation $\rightarrow$ incorrect
- C: Assertion true, Reason false $\rightarrow$ correct
- D: Both true, and Reason correct explanation $\rightarrow$ incorrect
Final conclusion

The correct option is:

$\boxed{\text{C}}$