Why is the extensive multi-step synthesis of aryl halides via benzenediazonium salt intermediates co — Haloalkanes and Haloarenes Chemistry Question

💡 Solution & Explanation

Direct halogenation of an arene (e.g., toluene) typically yields an inseparable mixture of ortho and para isomers due to the directing effects of existing substituents. In contrast, synthesizing via a diazonium salt involves nitration (often isomerically separable), reduction to an amine, and diazotization. The $-N_2^+$ group is an exceptional leaving group that is replaced exclusively at its exact location. This guarantees absolute positional control, allowing chemists to synthesize a pure ortho, meta, or para isomer without contamination from regional byproducts.