To differentiate between pentan -2-one and pentan -3-one a test is carried out. Which of the following is the correct answer?

Options

A. Pentan - 2 -one will give silver mirror test.
B. Pentan - 2 - one will give iodoform test.
C. Pentan - 3 - one will give iodoform test.
D. None of these.

Answer

To differentiate between pentan-2-one and pentan-3-one, we can use the Iodoform test, which is specific for methyl ketones. Here’s a step-by-step solution:

### Step 1: Understand the Structures
- **Pentan-2-one** has the structure:
\[ CH_3-CO-CH_2-CH_2-CH_3 \]
- **Pentan-3-one** has the structure:
\[ CH_3-CH_2-CO-CH_2-CH_3 \]

### Step 2: Identify the Functional Groups
- Both compounds are ketones, but we need to check if they contain a methyl group adjacent to the carbonyl group (C=O).
- **Pentan-2-one** has a methyl group (CH₃) directly attached to the carbonyl carbon, making it a methyl ketone.
- **Pentan-3-one** does not have a methyl group adjacent to the carbonyl carbon, thus it is not a methyl ketone.

### Step 3: Perform the Iodoform Test
- The Iodoform test is used to identify methyl ketones.
- Since pentan-2-one contains a methyl group adjacent to the carbonyl, it will give a positive Iodoform test (producing a yellow precipitate of iodoform, CHI₃).
- Pentan-3-one, lacking this methyl group, will not give a positive Iodoform test.

### Step 4: Conclusion
- **Pentan-2-one** will give a positive Iodoform test.
- **Pentan-3-one** will not give a positive Iodoform test.
- Therefore, the correct answer to differentiate between pentan-2-one and pentan-3-one is that pentan-2-one gives the Iodoform test, while pentan-3-one does not.

### Final Answer
The correct answer is that pentan-2-one gives a positive Iodoform test, while pentan-3-one does not.

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