`ArH + R -overset(O)overset(||)(C )-CI overset("Lewis acid")rarr Ar-overset(O)overset(||)(C )-R+HCI` is an example of

Options

A. Friedel-Craft alkylation
B. Friedel-Craft acylation
C. Cannizzaro reaction
D. Claisen condensation

Explanation

To solve the question, we need to analyze the given reaction step by step and identify what type of reaction it represents.

### Step-by-Step Solution:

1. **Understanding the Reactants**:
- The reactants are ArH (an aromatic compound) and R-C(=O)-Cl (an acyl chloride).
- ArH typically represents an aromatic hydrocarbon, where "Ar" signifies the aromatic ring and "H" indicates a hydrogen atom attached to it.

2. **Role of Lewis Acid**:
- A Lewis acid is a substance that can accept an electron pair. In this reaction, the Lewis acid facilitates the reaction between ArH and the acyl chloride.
- Common Lewis acids include AlCl3, BF3, etc., which can activate the acyl chloride by forming a complex.

3. **Mechanism of Reaction**:
- The Lewis acid interacts with the acyl chloride, making the carbonyl carbon more electrophilic.
- The aromatic compound (ArH) acts as a nucleophile and attacks the electrophilic carbon of the activated acyl chloride.

4. **Formation of the Product**:
- The result of this nucleophilic attack is the formation of an aromatic ketone (Ar-C(=O)-R).
- During this process, HCl is released as a byproduct.

5. **Identifying the Reaction Type**:
- This reaction is an example of **Friedel-Crafts acylation**. It is a type of electrophilic aromatic substitution where an acyl group is introduced into the aromatic ring.

### Final Answer:
The reaction `ArH + R-C(=O)-Cl (in the presence of Lewis acid) → Ar-C(=O)-R + HCl` is an example of **Friedel-Crafts acylation**.