On reaction of chlorobenzene with acetyl chloride in presence of AlC{{l}_{3}}, the major product formed is- (A) 1-Chloro-2-methylbenzene(B) 1-Chloro-4-ethylbenzene(C) 2-Chloro Acetophenone(D) 4-Chloro Acetophenone

To solve the question regarding the reaction of chlorobenzene with acetyl chloride in the presence of aluminum chloride (AlCl₃), we need to understand the mechanism of the reaction and the role of the reagents involved.

### Reaction Mechanism

1. **Formation of the Electrophile**:
- Chlorobenzene (C₆H₅Cl) does not react directly with acetyl chloride (CH₃COCl) because the chlorine atom is a poor leaving group. However, the presence of AlCl₃ facilitates the formation of an electrophile.
- Aluminum chloride coordinates with acetyl chloride, forming an acylium ion (\( CH₃CO^+ \)), which is a strong electrophile.

\[
\text{AlCl}_3 + \text{CH}_3COCl \rightarrow \text{CH}_3CO^+ + \text{AlCl}_4^-
\]

2. **Electrophilic Aromatic Substitution**:
- The acylium ion (\( CH₃CO^+ \)) attacks the aromatic ring of chlorobenzene, leading to electrophilic aromatic substitution.
- The chlorine atom, being a deactivating and ortho/para-directing group, influences the positions where the electrophile can attack. It is crucial to consider that while the reaction could potentially lead to substitution at multiple positions, the stability of the resulting carbocation and steric factors will determine the major product.

3. **Regeneration of the Aromatic Ring**:
- After the electrophile attaches to the ring, the aromatic character is restored by the loss of a proton, resulting in the formation of an acylated product.

### Expected Products
The two possible products from this reaction based on electrophilic substitution would be:

- **Acetophenone**: Formed when the acylium ion attaches to the aromatic ring, specifically at the para or ortho positions relative to the chlorine atom.
- **Chlorobenzene Derivatives**: If we were to consider further substitutions, products like 1-Chloro-2-methylbenzene or 1-Chloro-4-ethylbenzene are not formed in this context since the electrophile is the acylium ion, not a simple alkyl group.

### Analysis of Options
Given the choices:
- (A) 1-Chloro-2-methylbenzene
- (B) 1-Chloro-4-ethylbenzene
- (C) 2-Chloro Acetophenone
- (D) 4-Chloro Acetophenone

- The major product would likely be **acetophenone** (with a chlorine substituent still on the ring). However, since the options are structured with chlorinated acetophenones, we focus on options (C) and (D).
- The most stable product is **4-Chloro Acetophenone (D)**, as it would form preferentially due to less steric hindrance compared to 2-Chloro Acetophenone.

### Conclusion
The major product formed when chlorobenzene reacts with acetyl chloride in the presence of AlCl₃ is:

**(D) 4-Chloro Acetophenone.**