Question

What would be the major product A?

• A. figA
• B. figB
• C. figC
• D. figD

Hint:

Halogens are deactivating but ortho-para directing. In electrophilic substitution reactions, para products are often major because of lower steric hindrance.

Answer 1

The Correct Option is C

Concept: The reaction of an aromatic compound with an acyl chloride in the presence of anhydrous \(AlCl_3\) is known as Friedel-Crafts acylation. Halogens are deactivating but ortho-para directing substituents.

Step 1: Generate the electrophile.
Acetyl chloride reacts with \(AlCl_3\) to form the acylium ion. \[ CH_3COCl + AlCl_3 \rightarrow CH_3CO^+ + AlCl_4^- \] This acylium ion acts as the electrophile.

Step 2: Consider directing effect of chlorine.
The chlorine atom attached to benzene exhibits a \(-I\) effect but also donates electron density through resonance. Therefore chlorine directs incoming electrophiles mainly to the ortho and para positions.

Step 3: Compare ortho and para products.
Although both ortho and para products are formed, the para product experiences less steric hindrance. Consequently the para isomer predominates. \[ \boxed{\text{Para product is major}} \]

Step 4: Identify the product.
The acetyl group enters the para position with respect to chlorine. Hence the major product is: \[ \boxed{\text{4-Chloroacetophenone}} \]