What is the best method for the preparation of p-chlorotoluene in high yield?

The answer is: p-aminotoluene; NaNO₂/HCl, 0⁰C; CuCl

Explanation:

To prepare p-chlorotoluene from p-aminotoluene:

Diazotization reaction: This reaction is used form the preparation aryldiazonium salt from primary aromatic amines.

Therefore, p-aminotoluene is treated with NaNO₂/HCl at 0-5⁰C to prepare the aryl diazonium salt.

Sandmeyer reaction: This reaction is used for the preparation of aryl halides from aryl diazonium salts.

Therefore, the aryl diazonium salt formed by the diazotization reaction of p-aminotoluene, is heated with cuprous chloride to give p-chlorotoluene.