Sandmeyer Reaction: Diazonium → Aryl Halides/CN (Copper-Mediated Substitution)

Master the Sandmeyer reaction: replacing diazonium with Cl, Br, or CN using Cu(I) salts. Mechanistic outline, scope, and exam pitfalls.

• Reaction: Ar–N2+ → Ar–X (X=Cl, Br, CN)
• What it does: Installs halides or nitrile on aromatic ring
• Typical reagents: CuCl, CuBr, CuCN
• Key intermediate: Radical/copper pathway (often taught as single-electron steps)
• Driving force: Loss of N2 gas
• Exam type: Synthesis planning
• Exam type: Predict product