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 identify if any of them contain a methyl ketone structure. The iodoform test is specifically used to detect the presence of methyl ketones, which have the general structure R-CO-CH3.

Let's analyze each option step by step:

### Step 1: Understand the iodoform test
- The iodoform test is used to identify methyl ketones (R-CO-CH3).
- In this test, a methyl ketone reacts with iodine (I2) and a base (like NaOH) to produce a yellow precipitate of iodoform (CHI3).

### Step 2: Analyze the options
1. **3-Pentanone**:
- Structure: CH3-CH2-CO-CH2-CH3
- This is a ketone, but it is not a methyl ketone because the carbonyl group (C=O) is not attached to a methyl group (CH3). Therefore, it will **not** give a positive iodoform test.

2. **Formaldehyde**:
- Structure: HCHO
- Formaldehyde is an aldehyde, not a ketone, and does not have the methyl ketone structure. Therefore, it will **not** give a positive iodoform test.

3. **Butanone**:
- Structure: CH3-CO-CH2-CH3
- This compound has the structure of a methyl ketone (R-CO-CH3), where R is CH3. Therefore, it will give a positive iodoform test, resulting in the formation of iodoform (CHI3).

4. **Benzyl Alcohol**:
- Structure: C6H5-CH2OH
- Benzyl alcohol is an alcohol and does not contain a ketone group, let alone a methyl ketone structure. Therefore, it will **not** give a positive iodoform test.

### Conclusion
Among the given options, **butanone** is the only compound that will give a positive iodoform test.

### Final Answer
The correct answer is **Butanone**.

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