Why o-/p-NO₂ makes haloarenes react with OH⁻o-/p-NO₂ हैलोऐरीन को OH⁻ से क्रियाशील क्यों बनाता हैWhy o-/p-NO₂ makes haloarenes react with OH⁻
Class 12 Chemistry · Chapter 6 · interactive diagram
Parts and what they mean
- 1-Chloro-4-nitrobenzene (1-क्लोरो-4-नाइट्रोबेन्ज़ीन) — NO₂ (strongly electron-withdrawing) para to Cl.
- Hydroxide ion (nucleophile) (हाइड्रॉक्साइड आयन (नाभिकरागी)) — Adds to the carbon carrying Cl — easier because NO₂ withdraws electron density from the ring.
- Carbanion intermediate (कार्बऋणायन मध्यवर्ती) — C-1 now carries both Cl and OH (sp³). The negative charge is spread over the ring by resonance.
- Negative charge ortho to C-1 (C-1 के ऑर्थो पर ऋण आवेश) — One resonance structure.
- Negative charge para to C-1 — on the carbon bearing NO₂ (C-1 के पैरा पर ऋण आवेश — NO₂ वाले कार्बन पर) — Because the charge reaches the C–NO₂ carbon, it can move onto NO₂.
- Negative charge on an oxygen of NO₂ (NO₂ के ऑक्सीजन पर ऋण आवेश) — Extra, very stable structure (charge on electronegative O) — this is how o-/p-NO₂ stabilises the carbanion.
- Negative charge at the other ortho carbon (दूसरे ऑर्थो कार्बन पर ऋण आवेश) — Fourth structure.
- 4-Nitrophenoxide ion (4-नाइट्रोफ़ीनॉक्साइड आयन) — Cl⁻ leaves and the ring becomes aromatic again.
- 4-Nitrophenol (after acidification) (4-नाइट्रोफ़ीनॉल (अम्लीकरण के बाद)) — NCERT: (i) NaOH, 443 K (ii) H⁺. Compare chlorobenzene alone: 623 K and 300 atm.
- Conditions (परिस्थितियाँ) — Much milder than for chlorobenzene (623 K, 300 atm).
- Why m-NO₂ has no effect (m-NO₂ का प्रभाव क्यों नहीं) — With NO₂ meta, the negative charge never sits on the carbon bearing NO₂, so NO₂ cannot stabilise it (NCERT).
Original diagram drawn by Simple Learning Hub, based on the NCERT textbook. Report a mistake