- Exam
- JEE Main
- Year
- 2023
- Date
- 30 January
- Shift
- Morning Shift
- Subject
- Chemistry
- Chapter
- Biomolecules
JEE Main 2023 · 30 January · Morning Shift · Chemistry · Biomolecules
Given below are two statements: one is labelled as Assertion (A)...
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 -elimination followed by formation of furfural.
In the light of the above statements, choose the correct answer from the options given below:
Options
- A(A) is false but (R) is true
- BBoth (A) and (R) are true and (R) is the correct explanation of (A)
- C(A) is true but (R) is false
- DBoth (A) and (R) are true but (R) is not the correct explanation of (A)
Correct answer
C. (A) is true but (R) is false
Step-by-step solution
Seliwanoff 's test is a differentiating test for Ketose and aldose. This test relies on the principle that the keto hexose are more rapidly dehydrated to form -hydroxy methyl furfural when heated in acidic medium which on condensation with resorcinol, Cherry red or brown red coloured complex is formed rapidly indicating a positive test.
Aldoses take longer time to produce colour because under the same conditions, aldoses form furfural slowly, probably because β-elimination is required before dehydration to furfural. Therefore prolonged heating should be avoided.
Hence, Assertion is true but Reason is false.