Acetone reacts with phosphorous pentachloride to give:

Options

A. Vic-dihalide
B. `alpha, alpha` -dihalide
C. Gem-dihalide
D. `alpha, omega`- dihalide

Answer

To determine the product of the reaction between acetone and phosphorus pentachloride (PCl5), we can follow these steps:

### Step 1: Identify the Structure of Acetone
Acetone is a ketone with the molecular formula \( \text{C}_3\text{H}_6\text{O} \). Its structure can be represented as:
\[ \text{CH}_3\text{C}(=O)\text{CH}_3 \]

### Step 2: Understand the Reaction with PCl5
When acetone reacts with phosphorus pentachloride, chlorination occurs at the carbonyl carbon (the carbon atom double-bonded to oxygen). The oxygen atom in the carbonyl group will be displaced by chlorine.

### Step 3: Mechanism of the Reaction
1. **Formation of a Chloronium Ion**: The oxygen atom in acetone attacks phosphorus in PCl5, leading to the formation of a chloronium ion and the release of a chloride ion (Cl⁻).

\[ \text{CH}_3\text{C}(=O)\text{CH}_3 + \text{PCl}_5 \rightarrow \text{CH}_3\text{C}^+(Cl)\text{CH}_3 + \text{POCl}_3 + \text{Cl}^- \]

2. **Nucleophilic Attack**: The chloride ion (Cl⁻) acts as a nucleophile and attacks the positively charged carbon (the carbonyl carbon), resulting in the formation of a geminal dichloride.

\[ \text{CH}_3\text{C}^+(Cl)\text{CH}_3 + \text{Cl}^- \rightarrow \text{CH}_3\text{C}(Cl)(Cl)\text{CH}_3 \]

### Step 4: Identify the Product
The product formed is a geminal dichloride, where both chlorine atoms are attached to the same carbon atom (the carbonyl carbon). The structure of the product can be represented as:
\[ \text{CH}_3\text{C}(Cl)(Cl)\text{CH}_3 \]

### Conclusion
Thus, the reaction of acetone with phosphorus pentachloride yields a **geminal dihalide**.

### Final Answer
The product is a geminal dihalide.

---