Class 12 Organic Chemistry Short Notes
(CBSE 2025-26 • Current Syllabus Only)

• Preparation: Alcohol + HX/PCl₅/SOCl₂, Alkene + HX, Free radical halogenation
• SN1 vs SN2: SN1 → 3° > 2° > 1°, racemisation, polar solvent
  SN2 → 1° > 2° > 3°, inversion, polar aprotic
• Elimination: E2 (anti-periplanar, strong base), E1 (carbocation)
• Important conversions:
  • CH₃CH₂OH → CH₃CH₂Br → CH₃CH₂CN → CH₃CH₂COOH
  • C₆H₅Cl → C₆H₅OH (Dow process – NaOH, 623 K, 300 atm)
• Most repeated question: Why aryl halides less reactive in SN? (resonance + sp² carbon)

• Acidity order: Phenol > H₂O > Alcohol (resonance in phenoxide ion)
• Lucas Test: 3° → immediate turbidity, 2° → 5–10 min, 1° → no reaction
• Williamson Synthesis: RX + RONa → R–O–R' (best for unsymmetrical ethers)
• Important reactions:
  • Phenol → Salicylic acid (Kolbe-Schmitt)
  • Phenol → Salicylaldehyde (Reimer-Tiemann)
• Most asked: Mechanism of dehydration of alcohols

• Tests:
  • Tollens’ → silver mirror (aldehydes)
  • Fehling’s → red ppt (aldehydes)
  • Iodoform → CH₃CO– or CH₃CH(OH)–
• Named reactions:
  • Aldol condensation (α-H present)
  • Cannizzaro (no α-H)
  • HVZ (α-halogenation of acid)
• Most repeated conversion: Toluene → Benzoic acid → Benzaldehyde (Rosenmund)

• Basicity order (aqueous): 2° > 1° > 3° (solvation effect)
• Hinsberg Test:
  • 1° → soluble in alkali
  • 2° → insoluble
  • 3° → no reaction
• Carbylamine test: Only 1° amine → foul smell
• Most asked: Diazotization + Sandmeyer reaction

• Glucose: Open chain vs cyclic (pyranose/furanose), mutarotation
• Proteins: Peptide bond, zwitterion, denaturation
• Most repeated question: Structure of glucose & peptide linkage

• Addition: Polythene, PVC, Teflon
• Condensation: Nylon 6,6, Bakelite, Terylene
• Biodegradable: PHA, PLA
• Most asked: Difference between addition & condensation polymers

★ Tip: These 10 conversions appeared in almost every board paper (2020–2025)!