Which one of the following compounds cannot be used for the preparation of Grignard reagent

Options

A. `C_(2)H_(5)Br`
B. `HO-CH_(2)CH_(2)Cl`
C. `C_(6)H_(5)CH_(2)Cl`
D. `CH_(2)=CH-CH_(2)Cl`

Explanation

To determine which compound cannot be used for the preparation of a Grignard reagent, we need to analyze each option provided. A Grignard reagent is formed when an alkyl or aryl halide reacts with magnesium in dry ether. However, certain compounds cannot form Grignard reagents due to the presence of functional groups that can react with the Grignard reagent or interfere with its formation.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- The options given are:
1. C2H5Br (Ethyl bromide)
2. HOCH2CH2Cl (2-Chloroethanol)
3. CH3CH2Cl (Ethyl chloride)
4. CH2=CH-CH2Cl (3-Chloropropene)

2. **Analyze Each Compound**:
- **C2H5Br**:
- This is ethyl bromide. When reacted with magnesium in dry ether, it forms C2H5MgBr (Ethylmagnesium bromide), which is a Grignard reagent.

- **HOCH2CH2Cl**:
- This is 2-chloroethanol. The presence of the hydroxyl (-OH) group makes this compound reactive with Grignard reagents. If a Grignard reagent were formed from this compound, it would react with the -OH group to produce an alcohol instead of a Grignard reagent. Therefore, it cannot be used to prepare a Grignard reagent.

- **CH3CH2Cl**:
- This is ethyl chloride. When reacted with magnesium in dry ether, it forms CH3CH2MgCl (Ethylmagnesium chloride), which is a Grignard reagent.

- **CH2=CH-CH2Cl**:
- This is 3-chloropropene. When reacted with magnesium in dry ether, it forms CH2=CH-CH2MgCl (3-Chloropropylmagnesium chloride), which is also a Grignard reagent.

3. **Conclusion**:
- The compound that cannot be used for the preparation of a Grignard reagent is **HOCH2CH2Cl (2-Chloroethanol)** because the hydroxyl group will react with the Grignard reagent instead of allowing its formation.

### Final Answer:
**HOCH2CH2Cl (2-Chloroethanol)** cannot be used for the preparation of a Grignard reagent.