Why Does Proline Not Give a Positive Test with Ninhydrin

question 23

Multiple Choice

Why does proline not give a positive test with ninhydrin?

• A) The secondary amine of proline is too weak a nucleophile to add to ninhydrin.
• B) The of the ammonium in proline (10.6) is too high to react with ninhydrin.
• C) Hydrolysis of the second imine in the reaction mechanism cannot occur with proline.
• D) The first imine cannot form in the reaction between proline and ninhydrin.
• E) The second imine formed by decarboxylation in the mechanism is too unstable to form.

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