Which reagent can be used to convert a carboxylic acid chloride into a ketone ?

Options

A. Chromic acid
B. PCP
C. Diborane , hydrogen peroxide
D. An organolithium compound

Answer

To convert a carboxylic acid chloride into a ketone, we can use an organolithium compound, specifically a reagent known as Gilman reagent (R2CuLi). Here’s a step-by-step breakdown of the process:

### Step 1: Identify the Reactants
- The starting material is a carboxylic acid chloride, which can be represented as RCOCl.
- We need to find a suitable reagent that can facilitate the conversion to a ketone.

### Step 2: Analyze the Given Reagents
- **Chromic Acid**: This is primarily used for oxidizing alcohols to ketones, not for converting acid chlorides to ketones.
- **PCP**: This is a drug and not relevant for this conversion.
- **Diborane and Hydrogen Peroxide**: These are used for hydroboration-oxidation processes, which do not apply here.
- **Organolithium Compounds (Gilman Reagent)**: This is the correct choice as it can react with acid chlorides to form ketones.

### Step 3: Reaction Mechanism
1. **Nucleophilic Attack**: The organolithium compound (R2CuLi) acts as a nucleophile. The carbon atom in the acid chloride (RCOCl) is electrophilic due to the presence of the electronegative chlorine atom.
2. **Formation of Tetrahedral Intermediate**: The nucleophile attacks the carbonyl carbon, leading to the formation of a tetrahedral intermediate.
3. **Leaving Group Departure**: The oxygen in the intermediate can donate its electrons back, facilitating the departure of the chloride ion (Cl-) as a good leaving group.
4. **Formation of Ketone**: The final product is the ketone (RCO-R') along with by-products (R'Cu and LiCl).

### Step 4: Write the Overall Reaction
The overall reaction can be summarized as:
\[ RCOCl + R2CuLi \rightarrow RCO-R' + R'Cu + LiCl \]

### Conclusion
Thus, the reagent that can be used to convert a carboxylic acid chloride into a ketone is an **organolithium compound** (Gilman reagent).

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