Ninhydrin reagent reacts with acids to give a purple colour. In the reaction of ninhydrin with phenylalanine, which of the following is responsible for this colour ?

Options

A.
B.
C.
D.

Explanation

To solve the question regarding the reaction of ninhydrin with phenylalanine and the source of the purple color produced, we can break down the process step by step.

### Step-by-Step Solution:

1. **Understanding Ninhydrin**:
- Ninhydrin is a chemical reagent with the formula C9H6O4, also known as 2,2-dihydroxyindane-1,3-dione. It is commonly used to detect amino acids.

**Hint**: Recall the chemical structure and properties of ninhydrin, as it is crucial for understanding its reaction with amino acids.

2. **Reaction with Amino Acids**:
- Ninhydrin reacts with alpha amino acids, which include phenylalanine. In this reaction, ninhydrin interacts with the amino group (-NH2) of the amino acid.

**Hint**: Focus on the functional groups present in amino acids and how they interact with reagents like ninhydrin.

3. **Formation of the Colored Compound**:
- When ninhydrin reacts with phenylalanine, it forms a colored compound. The reaction involves the deamination of the amino acid and the formation of a complex that exhibits a purple color.

**Hint**: Consider the chemical changes that occur during the reaction and the types of products formed.

4. **Identifying the Source of Color**:
- The purple color observed in the ninhydrin test is primarily due to the formation of a specific compound known as Ruhemann's purple. This compound results from the reaction of ninhydrin with the amino acid.

**Hint**: Remember the name of the colored compound formed in the reaction, as it directly answers the question.

5. **Conclusion**:
- Therefore, in the reaction of ninhydrin with phenylalanine, the purple color is due to the formation of Ruhemann's purple, which is the product of the reaction between ninhydrin and the amino group of phenylalanine.

**Hint**: Ensure you can connect the chemical reaction to the visual outcome (color change) in the ninhydrin test.

### Final Answer:
The purple color observed in the reaction of ninhydrin with phenylalanine is due to the formation of Ruhemann's purple, which is the product of the reaction between ninhydrin and the amino acid.