Question

What is the major product of the following Friedel-Crafts alkylation of chlorobenzene is

• A.
• B.
• C.
• D.

Hint:

Ortho/para directing groups favor the para position if steric hindrance exists at the ortho position.

Answer 1

The Correct Option is B

Reaction Mechanism:

• Friedel-Crafts acylation involves introducing an acyl group (\( RCO \)) onto an aromatic ring. 
• The reaction uses an acyl chloride (\( RCOCl \)) and a Lewis acid catalyst (\( AlCl_3 \)).
• In this case, the reaction is:

\( C_6H_5Cl + CH_3COCl \xrightarrow{AlCl_3} C_6H_4Cl-CO-CH_3 \) (para-product)

Key Observations:

• Chlorine (\( Cl \)) is an electron-withdrawing group, but it directs substituents to the ortho and para positions due to its lone pair resonance effect.
• The para product is preferred over the ortho product because steric hindrance at the ortho position is minimized.

Final Product:

The major product of the reaction is para-chloroacetophenone (\( C_6H_4Cl-CO-CH_3 \)).