Which of the following will give iodoform test?

Options

A. 3-Pentanone
B. Formaldehyde
C. Butanone
D. Benzylalcohol

Answer

To determine which of the given compounds will give a positive iodoform test, we need to analyze each compound based on the criteria for the iodoform test. The iodoform test is positive for compounds that contain a methyl ketone group (C=O with a CH3 group) or for certain secondary alcohols that can be oxidized to form a methyl ketone.

### Step-by-Step Solution:

1. **Identify the Compounds:**
- The compounds given are:
1. 3-Pentanone
2. Formaldehyde
3. Butanone
4. Benzyl alcohol

2. **Analyze Each Compound:**
- **3-Pentanone (C5H10O):**
- Structure: CH3-CH2-CO-CH2-CH3
- This compound has a ketone functional group, but it is not a methyl ketone (the ketone is not attached to a CH3 group). Therefore, it will not give a positive iodoform test.

- **Formaldehyde (HCHO):**
- Structure: HCHO
- Formaldehyde is an aldehyde and does not contain a methyl ketone group. Thus, it will not give a positive iodoform test.

- **Butanone (C4H8O):**
- Structure: CH3-CO-CH2-CH3
- This compound has a methyl ketone group (C=O with a CH3 group). Therefore, it will give a positive iodoform test.

- **Benzyl Alcohol (C7H8O):**
- Structure: C6H5-CH2OH
- Benzyl alcohol is a primary alcohol. When oxidized, it would convert to benzaldehyde (C6H5CHO), which does not have a methyl ketone structure. Therefore, it will not give a positive iodoform test.

3. **Conclusion:**
- The only compound that will give a positive iodoform test is **Butanone (option 3)**.

### Final Answer:
**Butanone will give a positive iodoform test.**

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