For obtaining butan-2-one from acetyl chloride, which of the following reagent can be employed?

Options

A. Grignard reagent
B. Reaction with HI
C. `H_(2)//Pd//BaSO_(4)`
D. Reaction with `(C_(2)H_(5))_(2)Cd` in the presence of dry ether

Answer

To obtain butan-2-one from acetyl chloride, we need to analyze the given options and determine which reagent can facilitate this transformation. Let's break down the steps involved in this process:

### Step-by-Step Solution:

1. **Identify the Reactants and Products**:
- The starting material is **acetyl chloride**, which has the structure CH₃C(=O)Cl.
- The target product is **butan-2-one**, which has the structure CH₃C(=O)CH₂CH₃.

2. **Understand the Reaction Requirements**:
- To convert acetyl chloride (which has 2 carbon atoms) into butan-2-one (which has 4 carbon atoms), we need to add 2 carbon atoms to the molecule.

3. **Evaluate Each Option**:
- **Option A: Grignard Reagent**:
- Grignard reagents react with carbonyl compounds to form alcohols. If we react acetyl chloride with a Grignard reagent, we would get a tertiary alcohol, which would require further oxidation to form butan-2-one. Therefore, this option is not suitable.

- **Option B: Reaction with HI**:
- Hydroiodic acid (HI) does not increase the carbon chain length. It can only replace functional groups, so it cannot convert acetyl chloride into butan-2-one. This option is also not suitable.

- **Option C: H₂/Pd (Hydrogenation)**:
- This reaction would reduce the carbonyl group but would not add any carbon atoms to the structure. It would not yield butan-2-one from acetyl chloride. Thus, this option is not suitable.

- **Option D: Diethyl Cadmium in the presence of Dry Ether**:
- Diethyl cadmium (C₂H₅)₂Cd is a reagent that can add two carbon atoms to the acetyl chloride. The reaction mechanism involves the nucleophilic attack of the ethyl group on the carbonyl carbon of acetyl chloride, displacing the chloride ion and forming butan-2-one. This option is suitable.

4. **Conclusion**:
- The correct reagent to convert acetyl chloride to butan-2-one is **diethyl cadmium in the presence of dry ether** (Option D).

### Final Answer:
The correct option is **D: Diethyl cadmium in the presence of dry ether**.

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