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🚨 99% Students FAIL These 17 Reactions! 🧪
CBSE Class 12 Chemistry Topper's Secret Sheet (2026 Board Exam) | Guaranteed 95+ Marks Strategy
⚠️ CRITICAL EXAM ALERT: These 17 name reactions account for 15-20 Marks directly in the CBSE Board Paper (2020-2025 analysis). Missing these means losing GUARANTEED marks! Updated for 2026 syllabus.
Chapter 1
Chapter 2
⭐ Chapter 3
Chapter 4
Chapter 5
📚 Why This List is Your Secret Weapon
Based on NCERT Class 12 Chemistry syllabus and analysis of 10 years of CBSE board papers (2016-2025), these name reactions appear in:
- ✅ 3/5-mark questions (direct reaction writing)
- ✅ Conversion problems (multi-step synthesis)
- ✅ Mechanism-based questions (electron movement)
- ✅ Distinguish tests (Tollens', Fehling's, Iodoform)
🎯 Pro Strategy: Revise 3 reactions daily using spaced repetition. Write each reaction 5 times with conditions. You'll master all 17 in under a week!
1️⃣ Haloalkanes & Haloarenes
| Reaction | Reagents/Conditions | Key Product | Priority |
|---|---|---|---|
| Finkelstein | NaI + dry acetone | Alkyl iodide (R-I) | ⭐⭐ |
| Swarts | AgF / Hg₂F₂ / CoF₂ / SbF₃ | Alkyl fluoride (R-F) | ⭐⭐ |
| Wurtz | 2R-X + 2Na + dry ether | Symmetrical Alkane (R-R) | ⭐⭐⭐ |
| Wurtz-Fittig | Ar-X + R-X + 2Na + dry ether | Alkylarene (Ar-R) | ⭐⭐ |
| Fittig | 2Ar-X + 2Na + dry ether | Biaryl (Ar-Ar) | ⭐ |
🔍 Visual Memory Aid:
Wurtz: CH₃-Br + Br-CH₃ → CH₃-CH₃ (Ethane)
Think: "Two halides join hands with sodium in dry ether!"
Wurtz: CH₃-Br + Br-CH₃ → CH₃-CH₃ (Ethane)
Think: "Two halides join hands with sodium in dry ether!"
2️⃣ Alcohols, Phenols & Ethers
| Reaction | Reagents/Conditions | Key Product | Priority |
|---|---|---|---|
| Kolbe's Reaction | Phenol + NaOH → CO₂ (135°C, 4-7 atm) | Salicylic Acid (o-Hydroxybenzoic acid) | ⭐⭐⭐ |
| Reimer-Tiemann | Phenol + CHCl₃ + aq. NaOH (60°C) | Salicylaldehyde (o-Hydroxybenzaldehyde) | ⭐⭐⭐ |
| Williamson Synthesis | R-O⁻Na⁺ + R'-X → dry ether | Ether (R-O-R') | ⭐⭐⭐ |
| Dows Process | Chlorobenzene + aq. NaOH (300°C, 200 atm) | Phenol | ⭐ |
💡 Exam Hack: Kolbe's gives ortho product due to electrophilic substitution. Reimer-Tiemann also gives ortho due to -OH directing effect.
3️⃣ Aldehydes & Ketones (⭐⭐⭐⭐ HIGHEST WEIGHTAGE)
🎯 Chapter Alert: This chapter contributes 8-12 marks in CBSE papers. Master these reactions for guaranteed marks!
💡 Critical Distinction:
Clemmensen: Zn-Hg + conc. HCl → Acidic medium
Wolff-Kishner: NH₂NH₂ + KOH/glycol, Δ → Basic medium
Both reduce C=O to CH₂. Choose based on other functional groups present!
Clemmensen: Zn-Hg + conc. HCl → Acidic medium
Wolff-Kishner: NH₂NH₂ + KOH/glycol, Δ → Basic medium
Both reduce C=O to CH₂. Choose based on other functional groups present!
✨ IODOFORM REACTION [NEW ADDITION] ⭐⭐⭐
R-CO-CH₃ + I₂ + NaOH → CHI₃↓ (Yellow ppt) + R-COONa
Visual:
O O
|| ||
R-C-CH₃ → R-C-O⁻Na⁺ + CHI₃↓ (yellow, antiseptic smell)
O O
|| ||
R-C-CH₃ → R-C-O⁻Na⁺ + CHI₃↓ (yellow, antiseptic smell)
Tests POSITIVE for:
✓ CH₃-CO-R (Methyl ketones)
✓ CH₃-CH(OH)-R (Methyl carbinols)
✓ Ethanol (CH₃CH₂OH) & Acetaldehyde (CH₃CHO)
Exam Tip: Distinguishes acetone from propanal! Write "yellow ppt of CHI₃" for full marks.
✓ CH₃-CO-R (Methyl ketones)
✓ CH₃-CH(OH)-R (Methyl carbinols)
✓ Ethanol (CH₃CH₂OH) & Acetaldehyde (CH₃CHO)
Exam Tip: Distinguishes acetone from propanal! Write "yellow ppt of CHI₃" for full marks.
✨ STEPHEN REACTION [NEW ADDITION] ⭐⭐
R-C≡N + SnCl₂ + HCl → (then H₂O) → R-CHO
Visual:
N
||
R-C≡N → [R-CH=NH]⁺Cl⁻ → R-CH=O
N
||
R-C≡N → [R-CH=NH]⁺Cl⁻ → R-CH=O
Note: Selective reduction of nitriles to aldehydes.
Alternative: DIBAL-H also used for same conversion.
Exam Tip: Specify "SnCl₂ + HCl" NOT just "reduction" for full credit.
Alternative: DIBAL-H also used for same conversion.
Exam Tip: Specify "SnCl₂ + HCl" NOT just "reduction" for full credit.
| Reaction | Reagents/Conditions | Key Product | Priority |
|---|---|---|---|
| Aldol Condensation | Dil. NaOH/KOH, α-H present | β-Hydroxy carbonyl → α,β-unsaturated | ⭐⭐⭐⭐ |
| Cannizzaro | Conc. NaOH, No α-H (e.g., HCHO, C₆H₅CHO) | Alcohol + Carboxylate Salt (disproportionation) | ⭐⭐⭐ |
| Clemmensen | Zn-Hg + conc. HCl | C=O → CH₂ | ⭐⭐⭐ |
| Wolff-Kishner | NH₂NH₂ + KOH/glycol, Δ | C=O → CH₂ | ⭐⭐⭐ |
| Rosenmund | H₂ / Pd-BaSO₄ (poisoned) | Acid Chloride → Aldehyde | ⭐⭐ |
| Etard | CrO₂Cl₂ (chromyl chloride) + toluene | Benzaldehyde from methylbenzene | ⭐⭐ |
| Gattermann-Koch | CO + HCl + AlCl₃/CuCl + benzene | Benzaldehyde | ⭐⭐ |
| Tollens' Test | [Ag(NH₃)₂]⁺, warm | Silver mirror (Aldehydes ONLY) | ⭐⭐ |
| Fehling's Test | Fehling A+B, warm | Red ppt. Cu₂O (Aliphatic aldehydes ONLY) | ⭐ |
4️⃣ Carboxylic Acids & Derivatives
| Reaction | Reagents/Conditions | Key Product | Priority |
|---|---|---|---|
| Hell-Volhard-Zelinsky (HVZ) | X₂ (Cl₂/Br₂) + red P | α-Halo carboxylic acid | ⭐⭐⭐ |
| Esterification | RCOOH + R'OH + conc. H₂SO₄ (cat.) | Ester + H₂O | ⭐⭐ |
| Decarboxylation | RCOONa + soda lime (NaOH+CaO), Δ | Alkane (R-H) + Na₂CO₃ | ⭐⭐ |
HVZ Visual Aid:
O O
|| ||
R-CH₂-C-OH → R-CH-C-OH
|
X
Note: α-halogenation; doesn't work for formic acid (no α-carbon)
O O
|| ||
R-CH₂-C-OH → R-CH-C-OH
|
X
Note: α-halogenation; doesn't work for formic acid (no α-carbon)
5️⃣ Amines (⭐ High Conversion Questions)
| Reaction | Reagents/Conditions | Key Product | Priority |
|---|---|---|---|
| Hoffmann Bromamide | RCONH₂ + Br₂ + 4NaOH | 1° Amine (1 Carbon less than amide) | ⭐⭐⭐⭐ |
| Carbylamine | 1° amine + CHCl₃ + alc. KOH, Δ | Foul-smelling isocyanide (R-NC) — Test for 1° amines | ⭐⭐⭐ |
| Diazotization | ArNH₂ + NaNO₂ + HCl (0-5°C) | Benzene diazonium salt (ArN₂⁺Cl⁻) | ⭐⭐⭐⭐ |
| Sandmeyer | ArN₂⁺Cl⁻ + CuX/HX (X = Cl, Br, CN) | Aryl halide/nitrile | ⭐⭐⭐ |
| Gattermann | ArN₂⁺Cl⁻ + Cu powder + HX | Aryl halide (modification of Sandmeyer) | ⭐⭐ |
| Balz-Schiemann | ArN₂⁺Cl⁻ + HBF₄ → ArN₂⁺BF₄⁻ → Δ | Aryl fluoride | ⭐ |
| Gabriel Phthalimide | Phthalimide + KOH → R-X → hydrolysis | Pure primary aliphatic amine | ⭐⭐⭐ |
| Hinsberg's Test | Amine + C₆H₅SO₂Cl | Distinguish 1°/2°/3° amines by solubility | ⭐⭐ |
✨ GABRIEL SYNTHESIS - VISUAL AID
Step-by-Step Visual:
Step 1: Phthalimide + KOH → Potassium phthalimide
Step 2: + R-X → N-Alkylphthalimide
Step 3: Hydrolysis → R-NH₂ + Phthalic acid
Skeleton:
O O
// //
O=C C=O + KOH → O=C C=O K⁺
\\ | \\ |
N-H N⁻
Note: Gives PURE primary aliphatic amines; FAILS for aryl halides
Step 1: Phthalimide + KOH → Potassium phthalimide
Step 2: + R-X → N-Alkylphthalimide
Step 3: Hydrolysis → R-NH₂ + Phthalic acid
Skeleton:
O O
// //
O=C C=O + KOH → O=C C=O K⁺
\\ | \\ |
N-H N⁻
Note: Gives PURE primary aliphatic amines; FAILS for aryl halides
🔄 High-Frequency Conversion Chains (Practice These!)
Master these pathways for 5-mark conversion questions:
- Alcohol → [PCC] → Aldehyde → [Tollens'] → Carboxylic Acid
- Alkyl Halide → [aq. KOH] → Alcohol → [Williamson] → Ether
- Benzene → [Cl₂/FeCl₃] → Chlorobenzene → [NaOH, 300°C] → Phenol → [Kolbe's] → Salicylic Acid
- Aniline → [NaNO₂/HCl, 0-5°C] → Diazonium → [CuCN] → Benzonitrile → [Stephen] → Benzaldehyde
- Aldehyde → [NaBH₄] → Alcohol → [SOCl₂] → Alkyl Halide → [KCN] → Nitrile → [LiAlH₄] → Amine
🎯 Pro Tip: For conversion questions, always write:
1. Reagents above the arrow
2. Conditions in brackets
3. Intermediate products if multi-step
Example: CH₃CHO → [NaBH₄] → CH₃CH₂OH → [SOCl₂] → CH₃CH₂Cl
1. Reagents above the arrow
2. Conditions in brackets
3. Intermediate products if multi-step
Example: CH₃CHO → [NaBH₄] → CH₃CH₂OH → [SOCl₂] → CH₃CH₂Cl
✍️ Exam Tips for Name Reactions (Score 95+)
- ✅ Write complete equations with reagents & conditions in brackets (marks deducted for incomplete answers)
- ✅ Understand mechanisms for Aldol, Cannizzaro, SN1/SN2, Electrophilic substitution
- ✅ Differentiate similar reactions: Clemmensen (acidic) vs Wolff-Kishner (basic); Sandmeyer (CuX) vs Gattermann (Cu powder)
- ✅ Note exceptions: Cannizzaro only for aldehydes without α-H; HVZ doesn't work for formic acid
- ✅ Use NCERT language: Board examiners prefer terminology from NCERT textbooks
- ✅ Draw skeletal structures: Even simple ones fetch extra marks in mechanism questions
- ✅ Time management: Spend max 3-4 minutes per 3-mark reaction question
🚫 Common Mistakes to Avoid:
• Writing "NaOH" instead of "dil. NaOH" or "conc. NaOH"
• Forgetting temperature conditions (0-5°C for Diazotization)
• Not specifying "dry ether" for Wurtz/Williamson reactions
• Confusing Tollens' (all aldehydes) vs Fehling's (aliphatic aldehydes only)
• Writing "NaOH" instead of "dil. NaOH" or "conc. NaOH"
• Forgetting temperature conditions (0-5°C for Diazotization)
• Not specifying "dry ether" for Wurtz/Williamson reactions
• Confusing Tollens' (all aldehydes) vs Fehling's (aliphatic aldehydes only)
⚡ Last-Minute Revision: Top 17 Must-Know Reactions
1. Aldol Condensation
2. Cannizzaro Reaction
3. Hoffmann Bromamide ⭐
4. Diazotization ⭐
5. Reimer-Tiemann
6. Kolbe's Reaction
7. Williamson Synthesis
8. Iodoform Reaction ✨
9. Clemmensen Reduction
10. Wolff-Kishner
11. Stephen Reaction ✨
12. HVZ Reaction
13. Gabriel Synthesis
14. Carbylamine Test
15. Sandmeyer Reaction
16. Tollens'/Fehling's Tests
17. Wurtz/Wurtz-Fittig