Arrange the following compounds in decreasing order of the ortho / para product ratio obtained upon reaction with Br ₂ / FeBr ₃ : (I) (II) (III)

Step-by-step solution

The reaction of the given alkylbenzenes with Br ₂ / FeBr ₃ is an electrophilic aromatic substitution (bromination). Alkyl groups are activating and ortho / para directing. The ratio of ortho to para products depends primarily on the steric hindrance caused by the alkyl group present on the benzene ring. As the size (steric bulk) of the alkyl group increases, it increasingly blocks the ortho positions, making the attack of the incoming electrophile ( Br ⁺ ) at the ortho position more difficult. Consequently, the pro