Observation of “Rhumann’s purple” is a confirmatory test for the presence of :

Biomolecules PYQ — JEE Main 2016 · 10 Apr · Shift 1 · Q1 with Solution

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Correct answer: C

Identify the test mentioned

“Rhumann’s purple” refers to Ruhemann’s purple, the deep violet/purple colored compound formed in the ninhydrin test.
What does ninhydrin test detect?

Ninhydrin reacts with free amino groups present in amino acids and in proteins/peptides to give a purple color.

Hence, observation of Ruhemann’s purple is taken as a confirmatory indication of proteinaceous material (or amino acids).
Check the options
- A: Reducing sugar → detected by tests like Benedict’s or Fehling’s test, not Ruhemann’s purple.
- B: Cupric ion → not identified by this test.
- C: Protein → correct, since proteins contain amino groups and give the ninhydrin purple color test.
- D: Starch → starch is identified by the iodine test, not this test.
Final answer

Therefore, the confirmatory test showing “Ruhemann’s purple” indicates the presence of protein.

$\boxed{\text{C: Protein}}$

View written solutionFree

Correct answer: C

Identify the test mentioned

“Rhumann’s purple” refers to Ruhemann’s purple, the deep violet/purple colored compound formed in the ninhydrin test.
What does ninhydrin test detect?

Ninhydrin reacts with free amino groups present in amino acids and in proteins/peptides to give a purple color.

Hence, observation of Ruhemann’s purple is taken as a confirmatory indication of proteinaceous material (or amino acids).
Check the options
- A: Reducing sugar → detected by tests like Benedict’s or Fehling’s test, not Ruhemann’s purple.
- B: Cupric ion → not identified by this test.
- C: Protein → correct, since proteins contain amino groups and give the ninhydrin purple color test.
- D: Starch → starch is identified by the iodine test, not this test.
Final answer

Therefore, the confirmatory test showing “Ruhemann’s purple” indicates the presence of protein.

$\boxed{\text{C: Protein}}$