📋 Given Parameters & Problem Setup
Statement I Benzenediazonium salt is prepared by the reaction of aniline with nitrous acid at 273 - 278 K. It decomposes easily in the dry state.
Statement II Insertion of iodine into the benzene ring is difficult and hence iodobenzene is prepared through the reaction of benzenediazonium salt with KI.
Statement I: Diazotization is carried out at 0-5°C (273-278 K), and dry diazonium salt is notoriously explosive/decomposes easily (NCERT verbatim, TRUE)! Statement II: Direct iodination is reversible; reaction of ArN₂⁺Cl⁻ with KI is the standard synthesis of iodobenzene (NCERT verbatim, TRUE)! Both statements are CORRECT!
1 Examine Statement I: Diazotization of primary aromatic amines is conducted in ice-cold conditions (273–278 K). In the solid/dry state, benzenediazonium salts are thermally unstable and decompose explosively. NCERT text verbatim: "It decomposes easily in the dry state." Statement I is TRUE.
2 Examine Statement II: Direct electrophilic iodination of benzene is reversible due to generation of reducing agent HI (requires oxidants like HNO₃/HIO₄). Therefore, direct insertion of iodine is difficult. Treatment of benzenediazonium chloride with aqueous KI provides an efficient, non-catalytic route to iodobenzene: Ar-N₂⁺Cl⁻ + KI → Ar-I + KCl + N₂. Statement II is TRUE.
3 Conclusion: Both Statement I and Statement II are correct.
4 Select Option (1) in under 10 seconds!
🛡️ Why You Can 100% Trust This Shortcut: Arenediazonium Salts Stability and Displacement Reactions (NCERT Chemistry · Amines & Haloarenes).
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Candidates sometimes think Sandmeyer’s reaction requires Cu₂Cl₂ or Cu₂Br₂ for iodination too. For iodobenzene, NO copper catalyst is needed; simply warming with aqueous KI gives iodobenzene quantitatively!
🛡️ How to avoid the -1 mark: Remember: Sandmeyer uses Cu for Cl/Br, but KI alone is enough for Iodine!
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NEET Chemistry Core Syllabus · Amines Standard Benchmark
Core Scientific Principle Tested:
"Diazotization occurs at 273-278 K; dry salt decomposes; KI readily yields iodobenzene."
Syllabus Focus: Diazonium Salts: Preparation, Stability and Replacement by Iodine
Ice cold to make, explosive when dry, and simply add KI for Iodobenzene ⟹ Both statements TRUE!
