**Sandmeyer's reaction** prepares aryl halides from:
- Aryl alcohols + HX
- Aryl diazonium salts (Ar-N₂⁺) + CuX
- Direct halogenation
- Aldol condensation
Show answer and solution
Correct answer: B. Aryl diazonium salts (Ar-N₂⁺) + CuX
**Sandmeyer:** ArN₂⁺X⁻ + CuX ⟶ Ar-X + N₂ + CuX.
Diazonium salt (from aromatic amine + HNO₂) is decomposed in presence of Cu(I) halide.
Especially useful for fluorides (Balz-Schiemann variant) where direct halogenation fails.