Which of the following amino acids do not give purple colour on reaction with ninhydrin ?

Options

A. Proline
B. alanine
C. glycine
D. both A and B

Answer

To determine which amino acids do not give a purple color when reacted with ninhydrin, we need to understand the reaction of ninhydrin with different amino acids.

### Step-by-Step Solution:

1. **Understanding Ninhydrin Reaction**:
- Ninhydrin reacts with amino acids to form a colored complex. Typically, most amino acids produce a purple color when they react with ninhydrin due to the formation of a specific complex.

2. **Identifying Common Amino Acids**:
- Common amino acids that react with ninhydrin include glycine, alanine, and many others. These generally yield a purple color.

3. **Analyzing Proline**:
- Proline is an amino acid that has a cyclic structure. When proline reacts with ninhydrin, it does not form the typical purple complex. Instead, it forms a yellow-orange product.

4. **Conclusion**:
- Since proline is the amino acid that does not produce a purple color upon reaction with ninhydrin, we can conclude that proline is the answer to the question.

### Final Answer:
- The amino acid that does not give a purple color on reaction with ninhydrin is **Proline**.

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