Which the following does not respond to iodoform reaction ?

Options

A. `(CH_3)_2CHCH(OH)CH_3`
B. `PhCH_2CHOHCH_3`
C. `phCH(OH)CH_2CH_3`
D. `CH_3CH_2OH`

Answer

To determine which of the given compounds does not respond to the iodoform reaction, we need to understand the conditions under which a compound will give a positive iodoform test. The iodoform reaction is characteristic of methyl ketones (compounds with the structure RCOCH3) and some secondary alcohols that can be oxidized to methyl ketones.

### Step-by-Step Solution:

1. **Identify the Structure of Each Compound**:
- We need to analyze the structure of each compound provided in the options. The key is to look for the presence of the methyl group (CH3) directly attached to the carbonyl carbon (C=O) or to the carbon of a secondary alcohol that can be oxidized to a methyl ketone.

2. **Analyze Each Compound**:
- **Compound 1**: CH3-CHOH-CH3 (This is a secondary alcohol).
- Upon oxidation, it converts to a ketone (acetone, CH3COCH3), which has the structure required for a positive iodoform test.
- **Result**: Positive iodoform test.

- **Compound 2**: C6H5-CH2-CO-CH3 (This is a ketone with a phenyl group).
- The structure has a methyl group attached to the carbonyl carbon, which meets the criteria for a positive iodoform test.
- **Result**: Positive iodoform test.

- **Compound 3**: C6H5-CH2-CH2-CHOH (This is an alcohol).
- Here, the CH3 group is not directly attached to the carbonyl carbon; instead, it is part of a longer carbon chain (C2H5). Therefore, it does not meet the criteria for the iodoform reaction.
- **Result**: Negative iodoform test.

- **Compound 4**: CH3-CH(OH)-CH3 (This is also a secondary alcohol).
- Upon oxidation, it will convert to a ketone (acetone), which has the structure required for a positive iodoform test.
- **Result**: Positive iodoform test.

3. **Conclusion**:
- The only compound that does not respond to the iodoform reaction is **Compound 3** (C6H5-CH2-CH2-CHOH).

### Final Answer:
**Compound 3 does not respond to the iodoform reaction.**

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