Ninhydrin test is generally used for the detection of amino acids and proteins, yielding a characteristic blue-violet complex. Which of the following standard amino acids is a notable exception and fa

Question

Ninhydrin test is generally used for the detection of amino acids and proteins, yielding a characteristic blue-violet complex. Which of the following standard amino acids is a notable exception and fails to give this characteristic blue-violet color?

Prashant Kotian · Accepted Answer

Correct answer: C. The ninhydrin test relies on the reaction with free primary amino () groups to yield a blue-violet product known as Ruhemann's purple. Proline is an imino acid; its nitrogen is incorporated into a secondary amine ring structure. Thus, it lacks a free group and gives a yellow color instead of blue-violet.

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