The reaction of CO + HCl in the presence of `AlCl_3` with benzene to form benzaldehyde is called

Options

A. Meerwein - Ponndorf - Verley reaction
B. Cannizzaro reaction
C. Gatterman - Koch reaction
D. Bayer - Villeger reaction

Answer

To solve the question regarding the reaction of CO + HCl in the presence of AlCl3 with benzene to form benzaldehyde, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**:
- The reactants in this reaction are carbon monoxide (CO), hydrochloric acid (HCl), and benzene (C6H6).

2. **Identify the Catalyst**:
- The catalyst used in this reaction is anhydrous aluminum chloride (AlCl3). This catalyst is crucial for facilitating the electrophilic substitution reaction.

3. **Understand the Reaction Type**:
- The reaction involves the introduction of a carbonyl group (C=O) into the benzene ring, resulting in the formation of benzaldehyde (C6H5CHO).

4. **Recognize the Mechanism**:
- The mechanism involves the formation of an acylium ion from the reaction of CO and HCl in the presence of AlCl3. The acylium ion then acts as an electrophile and reacts with benzene to form benzaldehyde.

5. **Name the Reaction**:
- This specific reaction is known as the **Gatterman-Koch reaction**. It is a form of electrophilic aromatic substitution where an aldehyde is formed from an aromatic compound.

### Final Answer:
The reaction of CO + HCl in the presence of AlCl3 with benzene to form benzaldehyde is called the **Gatterman-Koch reaction**.

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