Class 12 Chemistry Named Reactions with Examples and Tricks
Class 12 Chemistry mein Named Reactions Organic Chemistry ka ek important topic hai. Board examination mein reactions ke naam, chemical equations, reagents, reaction conditions aur products ki understanding kaafi useful hoti hai. Agar aap Bihar Board ya CBSE Class 12 Chemistry ki preparation kar rahe hain, toh ye notes aapko important reactions revise karne mein help karenge.
Is article mein aapko Aldol Condensation, Cannizzaro Reaction, Reimer-Tiemann Reaction, Kolbe Reaction, Sandmeyer Reaction, Gabriel Phthalimide Synthesis, Hoffmann Bromamide Reaction aur doosri important named reactions examples ke saath milengi.
Quick Answer: Named Reactions Kya Hoti Hain?
Named reactions woh chemical reactions hain jinhe kisi scientist ya discoverer ke naam par jaana jaata hai. Class 12 Organic Chemistry mein in reactions ko identify karne ke liye reactants, reagent, reaction conditions aur final product ko samajhna zaroori hai. Examples: Aldol Condensation, Cannizzaro Reaction aur Sandmeyer Reaction.
Table of Contents
1. Named Reactions ko kaise samjhein?
Har named reaction ko yaad karne ke liye sirf uska naam ratna enough nahi hai. In 4 points par focus karein:
1. Reactant
Starting compound kaun sa hai?
2. Reagent
Kaunsa chemical reaction karwata hai?
3. Condition
Heat, base ya doosri condition kya hai?
4. Product
Final product kya banega?
Exam Tip: Reaction ke saath reagent aur major product bhi likhne ki practice karein. Sirf reaction ka naam likhne se complete answer nahi banta.
2. Aldehydes aur Ketones ki Important Named Reactions
Carbonyl compounds ki reactions mein reactants aur reaction conditions ko identify karna particularly important hai.
1. Aldol Condensation
Definition: Alpha-hydrogen wale aldehydes ya ketones dilute base ki presence mein beta-hydroxy carbonyl compound bana sakte hain. Aldol product dehydration se unsaturated carbonyl compound bhi bana sakta hai.
Example: Ethanal
2 CH₃CHO → CH₃CH(OH)CH₂CHO
Condition: Dilute NaOH; product 3-hydroxybutanal hai.
Heat par dehydration se CH₃CH=CHCHO + H₂O ban sakta hai.
Easy Trick: Aldol = Alpha-H present + dilute base. Yaad rakhein, condensation ke baad dehydration bhi ho sakti hai.
2. Cannizzaro Reaction
Definition: Aise aldehydes jinmein alpha-hydrogen nahi hota, concentrated alkali ki presence mein disproportionation kar sakte hain. Ek molecule oxidise hota hai aur doosra reduce.
Example: Benzaldehyde
2 C₆H₅CHO + NaOH → C₆H₅CH₂OH + C₆H₅COONa
Condition: Concentrated NaOH; products benzyl alcohol aur sodium benzoate hain.
Easy Trick: Cannizzaro = No alpha-H + concentrated base. Ek aldehyde se alcohol aur carboxylate salt milte hain.
3. Rosenmund Reduction
Definition: Acid chloride ko selectively reduce karke aldehyde banaya jaata hai.
C₆H₅COCl + H₂ → C₆H₅CHO + HCl
Reagent: H₂, poisoned Pd/BaSO₄ catalyst.
Easy Trick: Rosenmund = Acid chloride to aldehyde.
4. Clemmensen Reduction
Definition: Aldehydes aur ketones ke carbonyl group ko methylene group mein reduce kiya jaata hai.
C₆H₅COCH₃ → C₆H₅CH₂CH₃
Reagent: Zn(Hg)/concentrated HCl.
Easy Trick: Clemmensen = Acidic reduction.
5. Wolff-Kishner Reduction
Definition: Aldehydes aur ketones ke carbonyl group ko hydrazine aur strong base ki help se methylene group mein convert kiya jaata hai.
R₂C=O → R₂CH₂
Reagents: NH₂NH₂, KOH, heat.
Easy Trick: Wolff-Kishner = Basic reduction. Clemmensen se contrast yaad rakhein.
6. Haloform Reaction
Definition: Methyl ketones aur suitable compounds, jaise ethanal aur ethanol, iodine aur alkali ke saath iodoform reaction de sakte hain.
CH₃COCH₃ + 3 I₂ + 4 NaOH → CHI₃ + CH₃COONa + 3 NaI + 3 H₂O
Yellow precipitate: Iodoform (CHI₃).
Easy Trick: Iodoform test = Yellow precipitate. Methyl ketone group ko pehchanne mein useful hai.
3. Alcohols aur Phenols ki Important Reactions
7. Kolbe-Schmitt Reaction (Kolbe's Reaction of Phenol)
Definition: Sodium phenoxide, CO₂ ke saath pressure aur heat par react karke acidification ke baad salicylic acid deta hai.
C₆H₅ONa + CO₂ → o-HOC₆H₄COONa
Acidification → o-HOC₆H₄COOH
Final product: Salicylic acid (major ortho product under standard conditions).
Easy Trick: Phenoxide + CO₂ + acidification = Salicylic acid.
Note: Is reaction ko Kolbe-Schmitt reaction kehna clearer hai; ise Kolbe electrolysis se confuse na karein.
8. Reimer-Tiemann Reaction
Definition: Phenol ko CHCl₃ aur aqueous NaOH ke saath react karke acidification ke baad mainly ortho-hydroxybenzaldehyde milta hai.
Phenol + CHCl₃ + NaOH → o-Hydroxybenzaldehyde (after acidification)
Major product: Salicylaldehyde.
Easy Trick: Reimer-Tiemann = Phenol par CHO group introduce hota hai.
9. Williamson Ether Synthesis
Definition: Alkoxide ya phenoxide ion primary alkyl halide ke saath react karke ether bana sakta hai.
C₂H₅ONa + CH₃Br → CH₃OC₂H₅ + NaBr
Product: Methoxyethane.
Easy Trick: Alkoxide + suitable primary alkyl halide = Ether. Secondary aur tertiary halides mein elimination compete kar sakti hai.
4. Amines ki Important Named Reactions
10. Gabriel Phthalimide Synthesis
Definition: Primary aliphatic amines prepare karne ke liye phthalimide method use kiya ja sakta hai.
Potassium phthalimide primary alkyl halide ke saath react karta hai. Uske baad hydrolysis ya suitable cleavage se primary amine milti hai.
Potassium phthalimide + R–X → N-alkyl phthalimide → R–NH₂
Best remembered for primary aliphatic amines; aryl halides se normal SN2 method se aniline prepare nahi hoti.
Easy Trick: Gabriel = Primary aliphatic amine.
11. Hoffmann Bromamide Degradation
Definition: Primary amide ko Br₂ aur aqueous NaOH/KOH ke saath react karane par ek carbon kam wala primary amine milta hai.
CH₃CONH₂ + Br₂ + 4 NaOH → CH₃NH₂ + Na₂CO₃ + 2 NaBr + 2 H₂O
Acetamide se methylamine; carbon atoms ki count 2 se 1 ho jaati hai.
Easy Trick: Hoffmann = Amide to amine, one carbon less.
12. Sandmeyer Reaction
Definition: Aromatic diazonium salt ke diazonium group ko Cu(I) salts ki help se Cl, Br ya CN se replace kiya ja sakta hai.
C₆H₅N₂⁺Cl⁻ → C₆H₅Cl + N₂
Reagent: CuCl. Nitrogen gas release hoti hai.
Easy Trick: Sandmeyer = Diazonium salt + Cu(I) salt.
13. Diazotisation Reaction
Definition: Primary aromatic amine ko nitrous acid ke saath low temperature par react karane se diazonium salt banta hai.
C₆H₅NH₂ + NaNO₂ + 2 HCl → C₆H₅N₂⁺Cl⁻ + NaCl + 2 H₂O
Temperature: 0–5°C. Product: Benzenediazonium chloride.
Easy Trick: Aniline + NaNO₂/HCl + cold = Diazonium salt.
14. Carbylamine Reaction
Definition: Primary amines, chloroform aur alcoholic KOH ke saath heat karne par isocyanide bana sakte hain. Ye primary amines ka characteristic test hai.
C₆H₅NH₂ + CHCl₃ + 3 KOH → C₆H₅NC + 3 KCl + 3 H₂O
Product: Phenyl isocyanide, jisme unpleasant smell hoti hai.
Easy Trick: Carbylamine test = Primary amine only (under standard test conditions).
5. Haloalkanes aur Haloarenes ki Important Reactions
15. Wurtz Reaction
Definition: Alkyl halides sodium metal ke saath dry ether mein react karke higher alkane dete hain.
2 CH₃Br + 2 Na → C₂H₆ + 2 NaBr
Condition: Dry ether.
Easy Trick: Wurtz = Two alkyl groups join. Different alkyl halides se product mixture mil sakta hai.
16. Friedel-Crafts Alkylation
Definition: Benzene ko alkyl halide aur anhydrous Lewis acid catalyst ke saath react karke alkylbenzene banaya ja sakta hai.
C₆H₆ + CH₃Cl → C₆H₅CH₃ + HCl
Catalyst: Anhydrous AlCl₃. Product: Toluene.
Easy Trick: Friedel-Crafts alkylation = Benzene ring par alkyl group.
17. Finkelstein Reaction
Definition: Alkyl chloride ya bromide ko sodium iodide ke saath acetone mein react karake alkyl iodide banaya ja sakta hai.
R–Cl + NaI → R–I + NaCl
Condition: Acetone; reaction precipitation se drive ho sakti hai.
Easy Trick: Finkelstein = Halogen exchange to iodide.
18. Swarts Reaction
Definition: Suitable alkyl chlorides ya bromides ko fluorinating agents ki help se alkyl fluorides mein convert kiya ja sakta hai.
R–Br → R–F
Fluorinating reagent reaction conditions ke according select hota hai.
Easy Trick: Swarts = Fluorine introduce karna.
6. Named Reactions Quick Revision Table
Exam se pehle is table se reaction ka naam, reagent aur main transformation revise karein.
| Reaction | Important Reagent | Main Result |
|---|---|---|
| Aldol Condensation | Dilute base | Beta-hydroxy carbonyl compound |
| Cannizzaro | Concentrated NaOH/KOH | Alcohol + carboxylate salt |
| Rosenmund | H₂, Pd/BaSO₄ | Acid chloride to aldehyde |
| Clemmensen | Zn(Hg)/HCl | Carbonyl to CH₂ |
| Wolff-Kishner | NH₂NH₂, KOH, heat | Carbonyl to CH₂ |
| Kolbe-Schmitt | CO₂, pressure, acidification | Salicylic acid |
| Reimer-Tiemann | CHCl₃, NaOH | Salicylaldehyde (major) |
| Williamson | Alkoxide + alkyl halide | Ether |
| Gabriel Synthesis | Potassium phthalimide | Primary aliphatic amine |
| Hoffmann Bromamide | Br₂ + NaOH | Amine with one carbon less |
| Sandmeyer | CuCl/CuBr/CuCN | Diazonium group replacement |
| Diazotisation | NaNO₂ + HCl, 0–5°C | Diazonium salt |
| Carbylamine | CHCl₃ + alcoholic KOH | Isocyanide |
| Wurtz | Na, dry ether | Higher alkane |
| Friedel-Crafts | Alkyl halide, AlCl₃ | Alkylbenzene |
| Finkelstein | NaI, acetone | Alkyl iodide |
| Swarts | Fluorinating agent | Alkyl fluoride |
7. Chemistry Named Reactions Yaad Karne ki Easy Tricks
Trick 1: Similar Reactions ko Compare Karo
- Clemmensen: Acidic medium, Zn(Hg)/HCl.
- Wolff-Kishner: Basic medium, NH₂NH₂/KOH/heat.
- Dono mein aldehyde/ketone ka carbonyl group reduce hokar CH₂ ban sakta hai.
Trick 2: Reagent se Reaction Identify Karo
- CHCl₃ + NaOH + phenol → Reimer-Tiemann.
- CHCl₃ + alcoholic KOH + primary amine → Carbylamine.
- NaNO₂ + HCl at 0–5°C + primary aromatic amine → Diazotisation.
- Br₂ + NaOH + primary amide → Hoffmann Bromamide.
Trick 3: Product ko Yaad Rakho
- Kolbe-Schmitt → Salicylic acid.
- Reimer-Tiemann → Salicylaldehyde.
- Gabriel → Primary aliphatic amine.
- Hoffmann Bromamide → One carbon less.
- Wurtz → Higher alkane.
7-Day Revision Plan
| Day | Revision Target |
|---|---|
| Day 1 | Aldehydes and Ketones |
| Day 2 | Alcohols and Phenols |
| Day 3 | Amines and Diazonium Salts |
| Day 4 | Haloalkanes and Haloarenes |
| Day 5 | Reagents aur Reaction Conditions |
| Day 6 | Written Practice: Equations and Products |
| Day 7 | Self-Test and Mistake Revision |
8. Class 12 Chemistry Named Reactions: Practice Questions
Q1. Cannizzaro Reaction ke liye aldehyde mein kaunsi condition honi chahiye?
Answer: Aldehyde mein alpha-hydrogen nahi hona chahiye.
Q2. Reimer-Tiemann Reaction mein phenol se kaunsa major product milta hai?
Answer: Salicylaldehyde (o-hydroxybenzaldehyde).
Q3. Hoffmann Bromamide Reaction mein carbon atoms ki number kaise change hoti hai?
Answer: Product amine mein ek carbon atom kam hota hai.
Q4. Clemmensen Reduction mein kaunsa reagent use hota hai?
Answer: Zn(Hg) aur concentrated HCl.
Q5. Gabriel Phthalimide Synthesis ka main use kya hai?
Answer: Primary aliphatic amines prepare karna.
9. Board Exam Mein Named Reactions Kaise Likhein?
- Reaction ka correct naam likhein.
- Balanced chemical equation likhein.
- Reagent aur necessary conditions mention karein.
- Major product ka naam ya structure identify karein.
- Jahan applicable ho, reaction ki special condition jaise alpha-hydrogen absence ya one-carbon degradation likhein.
Important: Ye article revision resource hai, official question paper ya guaranteed exam prediction nahi. Bihar Board/CBSE ke latest syllabus aur prescribed textbook ke according apni final preparation karein.
10. Frequently Asked Questions (FAQs)
Q1. Class 12 Chemistry ki important named reactions kaun si hain?
Important revision reactions mein Aldol Condensation, Cannizzaro, Rosenmund Reduction, Clemmensen Reduction, Wolff-Kishner Reduction, Kolbe-Schmitt, Reimer-Tiemann, Williamson Ether Synthesis, Gabriel Phthalimide Synthesis, Hoffmann Bromamide aur Sandmeyer Reaction shamil hain. Apne current syllabus se inki relevance confirm karein.
Q2. Named reactions ko jaldi kaise yaad karein?
Har reaction ke liye four-column notes banayein: reactant, reagent, condition aur product. Similar reactions ko compare karein aur bina dekhe equations likhne ki daily practice karein.
Q3. Clemmensen aur Wolff-Kishner Reduction mein kya difference hai?
Dono carbonyl group ko CH₂ mein reduce kar sakte hain. Clemmensen mein Zn(Hg)/HCl acidic conditions use hoti hain, jabki Wolff-Kishner mein NH₂NH₂ aur strong base ke saath heating hoti hai.
Q4. Cannizzaro aur Aldol Reaction mein difference kya hai?
Aldol Reaction mein suitable alpha-hydrogen wale carbonyl compounds base ki presence mein carbon-carbon bond bana sakte hain. Cannizzaro Reaction mein alpha-hydrogen ke bina aldehyde concentrated alkali mein disproportionation karta hai.
Q5. Hoffmann Bromamide Reaction ka product kya hota hai?
Primary amide se ek carbon atom kam wala primary amine banta hai. Example: Acetamide se methylamine.
Q6. Reimer-Tiemann aur Kolbe-Schmitt Reaction mein kya difference hai?
Reimer-Tiemann mein phenol se mainly salicylaldehyde milta hai. Kolbe-Schmitt mein sodium phenoxide, CO₂ aur acidification ke baad mainly salicylic acid milta hai.
Q7. Kya named reactions ke saath reagents bhi yaad karne chahiye?
Haan. Reaction ka naam, reagent, condition aur product ek saath yaad karne se conversion questions aur product-identification questions solve karna easier hota hai.
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Class 12 Chemistry Named Reactions ko master karne ka best method hai reagents, reaction conditions aur products ko logically samajhna. Aldol, Cannizzaro, Reimer-Tiemann, Kolbe-Schmitt, Gabriel, Hoffmann Bromamide aur Sandmeyer jaise reactions ki regular written practice karein. Quick revision table se daily revise karein aur apne syllabus ke according textbook questions solve karein.
Student Reminder: Is page ko bookmark karein aur exam se pehle reaction equations aur conditions ka self-test zaroor karein.
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