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 the presence of a methyl ketone structure or specific secondary alcohols that can undergo the iodoform reaction. Here's a step-by-step solution:

### Step 1: Understand the Iodoform Test
The iodoform test is a qualitative test used to identify the presence of methyl ketones (compounds with the structure R-CO-CH3) or certain secondary alcohols that can be oxidized to methyl ketones.

### Step 2: Identify the Compounds
We need to analyze the given options to see if they contain a methyl ketone structure or are secondary alcohols that can yield a methyl ketone upon oxidation.

### Step 3: Analyze Each Option
1. **3-Pentanone (C5H10O)**:
- Structure: CH3-CH2-CO-CH2-CH3
- This compound has a ketone group, but it does not have a methyl ketone arrangement (R-CO-CH3). Therefore, it will not give a positive iodoform test.

2. **Formaldehyde (HCHO)**:
- This is an aldehyde and does not fit the criteria for the iodoform test. Only acetaldehyde (which is a methyl aldehyde) can give a positive test, but formaldehyde cannot. Thus, this option is also incorrect.

3. **Butanone (C4H8O)**:
- Structure: CH3-CO-CH2-CH3
- This compound has a methyl ketone structure (R-CO-CH3), thus it will give a positive iodoform test.

4. **Benzyl Alcohol (C6H5CH2OH)**:
- This is a primary alcohol and does not have the necessary structure to give a positive iodoform test. Therefore, this option is incorrect.

### Step 4: Conclusion
From the analysis, the only compound that will give a positive iodoform test is **Butanone (Option C)**.

### Final Answer
**The correct answer is: Butanone (Option C)**.

---