Answer
Diazotization and Iodination via Diazonium Salt
Step 1: Diazotization Reaction
Aniline reacts with nitrous acid (formed in situ from NaNO2 and HCl) at 273–278 K (0–5°C) to form benzenediazonium chloride, a highly reactive intermediate.
C₆H₅NH₂ + HNO₂ + HCl → C₆H₅N₂⁺Cl⁻ + 2H₂O
Note: Benzenediazonium chloride is unstable and can explode in dry form.
It is typically used immediately in solution.
Step 2: Substitution with Potassium Iodide (KI)
Direct iodination of benzene is not feasible due to its reversibility. Instead, in the Sandmeyer or Finkelstein reaction, KI displaces the diazonium group (N₂⁺) to yield iodobenzene.
C₆H₅N₂⁺Cl⁻ + KI → C₆H₅I + KCl + N₂↑
Key Points:
- Statement I: True – Benzenediazonium salt is unstable and explosive in dry form.
- Statement II: True – KI replaces N₂⁺ to form iodobenzene efficiently.