Struggling to decode the Naming Reactions in Organic Chemistry Class 12? You’re not alone! From Friedel-Crafts alkylation to Cannizzaro reaction, organic chemistry’s vast array of named reactions often feels like a maze. This guide is your ultimate roadmap to mastering all essential naming reactions in organic chemistry for Class 12. Designed for clarity, we break down complex mechanisms—like SN2 substitutions, Aldol condensations, and Hoffmann degradations—into bite-sized, exam-friendly explanations. With step-by-step diagrams, real-world examples, and pro tips to avoid common mistakes, you’ll not only ace your board exams but also build a rock-solid foundation for competitive tests like NEET and JEE. Let’s turn those reaction nightmares into confident, marks-boosting strengths!
Let’s dive in!
1. Haloalkanes and Haloarenes
is a combined Haloalkanes and Haloarenes schematic. It shows:
- Nucleophilic Substitution (SN2) on an alkyl halide (ethyl chloride).
- Elimination to form an alkene with a strong base.
- Haloarene (aryl halide) ring, highlighting reduced reactivity due to resonance.
Key Points:
- Haloalkanes (R–X): Polar C–X bond → susceptible to nucleophilic substitution (SN1 or SN2) and elimination.
- SN2 Example: CH3CH2Cl+OH− ⟶ CH3CH2OH+Cl−
- Elimination: CH3CH2Cl+KOH(alc.) ⟶ CH2=CH2+KCl+H2
- CH3CH2Cl+KOH(alc.)⟶CH2=CH2+KCl+H2O A strong base removes a β-hydrogen, forming an alkene.
- Haloarenes (Ar–X): The aromatic ring’s resonance stabilizes the C–X bond, making them far less reactive in nucleophilic substitution than haloalkanes.
Introduction: Haloalkanes (alkyl halides) are hydrocarbons where one or more hydrogen atoms are replaced by halogen atoms (F, Cl, Br, I). Haloarenes (aryl halides) have halogens attached directly to an aromatic ring, like chlorobenzene. These compounds are key in organic synthesis due to their reactivity.
Reactions:
- Nucleophilic Substitution: Haloalkanes undergo SN1 (two-step, for tertiary halides) or SN2 (one-step, for primary halides) reactions. Example: CH₃CH₂Cl + OH⁻ → CH₃CH₂OH + Cl⁻ (SN2).
- Elimination: Forms alkenes with a strong base. Example: CH₃CH₂Cl + KOH (alc.) → CH₂=CH₂ + KCl + H₂O.
- Haloarenes are less reactive due to resonance stabilizing the C-X bond.
2. Finkelstein Reaction
is a sample schematic showing the Finkelstein Reaction (the SN2 halide-exchange of ethyl chloride by iodide), generated in Python with Matplotlib. It illustrates:
- The overall reaction: CH₃CH₂Cl + NaI (acetone) ⟶ CH₃CH₂I + NaCl (ppt)
- The SN2 mechanism: iodide attacks the alkyl chloride from the back side, displacing chloride.
Introduction: This reaction converts alkyl chlorides or bromides to alkyl iodides using sodium iodide (NaI) in acetone. It’s a halide exchange reaction.
Mechanism: It’s an SN2 reaction. NaI provides I⁻, which displaces Cl⁻ or Br⁻. Example: CH₃CH₂Cl + NaI → CH₃CH₂I + NaCl.
Diagram: Show CH₃CH₂Cl with I⁻ approaching from behind, pushing Cl⁻ out. Na⁺ pairs with Cl⁻ to form NaCl precipitate.
Key Points: Works because NaCl/NaBr precipitates in acetone, driving the reaction forward.
3. Swarts Reaction
Here is a Swarts Reaction schematic (generated with Python and Matplotlib) illustrating the conversion of ethyl bromide to ethyl fluoride via silver fluoride (AgF):
Key Points:
- Overall reaction: CH₃CH₂Br + AgF → CH₃CH₂F + AgBr (solid)
- Mechanism: Coordination of Ag⁺ with Br⁻ facilitates halide exchange, transferring F⁻ to the alkyl chain. The AgBr byproduct precipitates out, driving the reaction forward.
Introduction: Converts alkyl chlorides/bromides to alkyl fluorides using metallic fluorides like AgF or Hg₂F₂.
Mechanism: Halogen exchange via coordination. Example: CH₃CH₂Br + AgF → CH₃CH₂F + AgBr.
Diagram: Draw CH₃CH₂Br with AgF nearby; show F⁻ replacing Br⁻, forming AgBr solid.
Key Points: Fluorides are tricky to make; this method avoids harsh conditions.
4. Wurtz Reaction
Here is the Wurtz Reaction schematic. It shows how two molecules of methyl chloride (CH₃Cl) couple in the presence of sodium (Na) in dry ether to form ethane (CH₃CH₃) and sodium chloride (NaCl):
Key Steps:
- Single Electron Transfer (SET) from sodium to the alkyl halide, forming a radical (or carbanion).
- Coupling of two radicals to form the new C–C bond.
- Byproduct: Na⁺ and Cl⁻ combine to give NaCL.
Introduction: Couples two alkyl halides to form a higher alkane using sodium metal in dry ether.
Mechanism: Na donates electrons, forming radicals that combine. Example: 2CH₃Cl + 2Na → CH₃CH₃ + 2NaCl.
Key Points: Works best with same alkyl halides; unsymmetrical mixes give multiple products.
5. Fittig Reaction
Above is a Fittig Reaction schematic. It shows the coupling of two aryl halides (here, chlorobenzene) in the presence of sodium (Na) in dry ether to form a biaryl compound (biphenyl), along with sodium chloride (NaCl):
Key Steps:
- Single Electron Transfer (SET) from Na to the aryl halide, forming an aryl radical (C₆H₅•) and releasing Cl⁻.
- Coupling of two aryl radicals to form biphenyl (C₆H₅–C₆H₅).
- Byproduct: Cl⁻ and Na⁺ combine to yield NaCl.
This reaction is analogous to the Wurtz Reaction, but specific to aromatic halides. It is most straightforward for symmetrical biaryl synthesis.
Introduction: Couples two aryl halides to form biaryl compounds using sodium in dry ether.
Mechanism: Similar to Wurtz. Example: 2C₆H₅Cl + 2Na → C₆H₅-C₆H₅ + 2NaCl.
Key Points: Specific to aromatic halides; yields symmetrical products.
6. Wurtz-Fittig Reaction
Here is the Wurtz–Fittig Reaction schematic. It illustrates how an aryl halide (C₆H₅Cl) and an alkyl halide (CH₃Cl) couple in the presence of sodium (Na) in dry ether to form an alkyl-substituted aromatic (toluene), with sodium chloride (NaCl) as a byproduct:
Key Points:
- Single Electron Transfer (SET) from sodium to each halide, generating radicals (C₆H₅•\text{C₆H₅•}C₆H₅• and CH₃•\text{CH₃•}CH₃•).
- Coupling of the aryl radical with the alkyl radical to yield toluene (C₆H₅CH₃\text{C₆H₅CH₃}C₆H₅CH₃).
- Side Products may form if other halides are present or under less controlled conditions. This reaction is essentially a hybrid of Wurtz (alkyl–alkyl) and Fittig (aryl–aryl) couplings.
Introduction: Combines an alkyl halide and an aryl halide to form an alkyl-substituted aromatic compound.
Mechanism: Radical coupling via Na. Example: C₆H₅Cl + CH₃Cl + 2Na → C₆H₅CH₃ + 2NaCl.
Diagram: Show benzene with Cl and CH₃Cl; radicals C₆H₅• and CH₃• join.
Key Points: Mix of Wurtz and Fittig; side products possible.
7. Sandmeyer Reaction
Below is the Sandmeyer Reaction schematic. It demonstrates the conversion of a diazonium salt (benzenediazonium chloride) into an aryl halide (chlorobenzene) in the presence of copper(I) chloride (CuCl):
Key Points:
- Overall Reaction: C₆H₅N₂⁺Cl⁻+CuCl ⟶ C₆H₅Cl+N₂↑
- Mechanism: Copper(I) helps replace the diazonium group (−N2+) with chloride (Cl−).
- Conditions: Usually performed at low temperatures (cold) to stabilize the diazonium salt.
- Outcome: Produces haloarenes efficiently, with nitrogen gas evolving as a byproduct.
Introduction: Converts diazonium salts (ArN₂⁺) to aryl halides using CuX (CuCl, CuBr).
Mechanism: Cu⁺ assists in replacing N₂ with X⁻. Example: C₆H₅N₂Cl + CuCl → C₆H₅Cl + N₂.
Diagram: Draw benzene with N₂⁺, CuCl releasing N₂ gas, attaching Cl.
Key Points: Needs cold conditions; versatile for haloarenes.
8. Gattermann Reaction
Above is the Gattermann Reaction schematic, showing how benzene is chlorinated via HCN + HCl in the presence of copper powder (Cu), without forming a diazonium salt:
Key Points:
- Overall Reaction: C6H6+HCN+HCl+Cu ⟶ C6H5Cl+NH4Cl
- Mechanism: In situ formation of an electrophilic chlorinating species from HCN and HCl, facilitated by Cu.
- Advantages:
- No diazonium salt needed (unlike the Sandmeyer Reaction).
- Copper acts as a catalyst.
- Potentially simpler for certain halides.
Introduction: Introduces a halogen to an aromatic ring using HCN and Cu powder, avoiding diazonium salts.
Mechanism: HCN + HCl forms a reactive intermediate. Example: C₆H₆ + HCN + HCl + Cu → C₆H₅Cl + NH₄Cl.
Diagram: Show benzene attacked by Cl from HCN/HCl mix, Cu catalyzing.
Key Points: Simpler than Sandmeyer for some halides.
9. Electrophilic Substitution Reaction
Below is a simplified schematic for Electrophilic Aromatic Substitution (EAS). It illustrates the chlorination of benzene as an example, where FeCl₃ helps generate the electrophile (Cl⁺):
Diagram Explanation:
- Overall Reaction: C6H6+Cl2→FeCl3C6H5Cl+HCl
- Mechanism:
- Step 1: The electrophile (Cl⁺) is generated, often via Lewis acid catalyst (FeCl₃).
- Step 2: Benzene donates electron density to Cl⁺, forming the sigma complex (arenium ion).
- Step 3: Deprotonation of the ring recovers aromaticity, yielding chlorobenzene.
- Key Points:
- Electron-rich ring is susceptible to electrophilic attack.
- FeCl₃ or other Lewis acids activate halogen molecules (Cl₂, Br₂, etc.) to form the strong electrophile.
- The ring is restored to aromaticity by losing a proton (H⁺).
Introduction: Aromatic compounds replace H with an electrophile (E⁺) like NO₂⁺, Cl⁺.
Mechanism: E⁺ attacks the ring, forming a carbocation intermediate, then H⁺ leaves. Example: C₆H₆ + Cl₂ (FeCl₃) → C₆H₅Cl + HCl.
Diagram: Draw benzene with Cl⁺ attacking, sigma complex, then H⁺ leaving.
Key Points: Ring’s electron-rich nature drives this; catalysts like FeCl₃ activate E⁺.
10. Friedel-Crafts Alkylation Reaction
Key Points:
- Overall Reaction: C6H6+R−Cl →AlCl3 C6H5R+HCl
- Mechanism:
- Step 1: AlCl₃ coordinates with R–Cl, forming an alkyl cation (R⁺) and AlCl4−.
- Step 2: The arenium ion forms when R⁺ attacks the ring, creating a non-aromatic carbocation intermediate.
- Step 3: Deprotonation at the ring recovers aromaticity, yielding the alkyl-substituted benzene.
- Rearrangements can occur if the initially formed carbocation can stabilize by shifting (e.g., hydride or alkyl shifts).
- Over-alkylation is also possible, because the new alkyl-substituted ring is often more reactive than benzene itself.
Introduction: Adds an alkyl group to an aromatic ring using RCl and AlCl₃.
Mechanism: AlCl₃ generates R⁺, which attacks the ring. Example: C₆H₆ + CH₃Cl (AlCl₃) → C₆H₅CH₃ + HCl.
Key Points: Can rearrange; multiple alkylations possible.
11. Friedel-Crafts Acylation Reaction
Above is a Friedel–Crafts Acylation schematic generated with Python and Matplotlib. It shows how an acyl chloride (RCOCl) reacts with benzene in the presence of AlCl₃ to form an aryl ketone. In the example, acetyl chloride (CH₃COCl) yields acetophenone (C₆H₅COCH₃).
It illustrates how an acyl chloride (RCOCl) reacts with benzene (C₆H₆) in the presence of AlCl₃ to form an aryl ketone (C₆H₅COR). In this mechanism:
- Acylium Ion Formation: RCOCl + AlCl₃ → [R–C≡O]⁺ + AlCl₄⁻
- Electrophilic Attack: The aromatic ring attacks the acylium ion, forming a sigma complex (arenium ion).
- Deprotonation: Restores aromaticity, yielding the aryl ketone.
- Mechanism
- Step 1: Acylium ion (R–C≡O+) forms via reaction of the acyl chloride with AlCl₃.
- Step 2: Electrophilic attack of the aromatic ring on the acylium ion, forming the arenium ion (sigma complex).
- Step 3: Deprotonation restores aromaticity, yielding the aryl ketone.
- Key Points
- The acylium ion is stable (no carbocation rearrangement).
- The ketone product is typically less reactive toward further Friedel–Crafts reactions.
Introduction: Adds an acyl group (RCO-) to an aromatic ring using RCOCl and AlCl₃.
Mechanism: Forms RCO⁺ electrophile. Example: C₆H₆ + CH₃COCl (AlCl₃) → C₆H₅COCH₃ + HCl.
Diagram: Draw CH₃COCl with AlCl₃, forming CH₃CO⁺ attacking benzene.
Key Points: No rearrangement; ketones formed are less reactive.
12. Alcohols, Phenols, and Ethers
Highlights
- Alcohol (R–OH)
- Example: Ethanol (CH₃CH₂OH).
- Dehydration forms an alkene (CH₂=CH₂) and water.
- Phenol (Ar–OH)
- Example: C₆H₅OH.
- Electrophilic Substitution (e.g., bromination to give p-bromophenol).
- Ether (R–O–R)
- Example: Dimethyl ether (CH₃OCH₃).
- Cleavage by HI yields alkyl halide (CH₃I) and an alcohol (CH₃OH).
Acidity: Phenols are more acidic than typical alcohols (due to resonance stabilization of the phenoxide ion).
Ethers are generally stable but can be cleaved by strong acids (e.g., HI)
Introduction: Alcohols (-OH on alkyl), phenols (-OH on aryl), and ethers (R-O-R) are oxygen-containing compounds with distinct reactivities.
Reactions:
- Alcohols: Dehydration (CH₃CH₂OH → CH₂=CH₂).
- Phenols: Electrophilic substitution (C₆H₅OH + Br₂ → C₆H₅OHBr).
- Ethers: Cleavage by HI (CH₃OCH₃ + HI → CH₃I + CH₃OH).
Key Points: Acidity: phenol > alcohol; ethers are stable but cleave with strong acids.
13. Hydroboration-Oxidation
Introduction: Converts alkenes to alcohols with anti-Markovnikov addition using BH₃ and H₂O₂.
Mechanism: BH₃ adds to double bond, H₂O₂ oxidizes. Example: CH₂=CH₂ → CH₃CH₂OH.
Diagram: Draw CH₂=CH₂ with BH₃ adding H and B, then OH replacing B.
Key Points: Opposite to acid-catalyzed hydration; syn-addition.
14. Esterification Reaction
Introduction: This reaction forms esters from a carboxylic acid and an alcohol, catalyzed by acid (like H₂SO₄).
Mechanism: The -OH from the acid and -H from the alcohol combine to form water, linking the rest into an ester. Example: CH₃COOH + CH₃CH₂OH → CH₃COOCH₂CH₃ + H₂O.
Diagram: Draw CH₃COOH with its C=O and OH, CH₃CH₂OH attacking, H₂O leaving, and the ester forming with C=O-O-CH₂CH₃.
Key Points: Reversible reaction; excess alcohol or removal of water drives it forward.
15. Reimer-Tiemann Reaction
Introduction: Introduces an aldehyde group (-CHO) to phenols using chloroform (CHCl₃) and a strong base (KOH).
Mechanism: CHCl₃ forms dichlorocarbene (:CCl₂), which attacks the phenol ring. Example: C₆H₅OH → C₆H₅OH-2-CHO (salicylaldehyde).
Diagram: Show phenol (benzene with OH), :CCl₂ attacking ortho position, turning into -CHO after hydrolysis.
Key Points: Ortho product dominates; involves a carbene intermediate.
16. Kolbe Reaction
Introduction: Converts phenols to salicylic acid (o-hydroxybenzoic acid) using CO₂ and NaOH under heat and pressure.
Mechanism: Phenoxide ion reacts with CO₂, adding -COOH ortho to -OH. Example: C₆H₅OH → C₆H₄(OH)COOH.
Diagram: Draw phenoxide (C₆H₅O⁻), CO₂ attacking ortho, protonation forming -COOH.
Key Points: Used to make aspirin precursors; specific to phenols.
17. Cumene Reaction
Introduction: Produces phenol and acetone from cumene (isopropylbenzene) via oxidation and cleavage.
Mechanism: Cumene + O₂ → cumene hydroperoxide, then H⁺ cleaves it. Example: C₆H₅CH(CH₃)₂ → C₆H₅OH + CH₃COCH₃.
Diagram: Show cumene with -CH(CH₃)₂, O₂ adding -OOH, then splitting into phenol and acetone.
Key Points: Industrial process; key for phenol production.
18. Williamson Reaction
Introduction: Synthesizes ethers from an alkoxide (RO⁻) and an alkyl halide.
Mechanism: SN2 reaction where RO⁻ displaces X⁻. Example: CH₃CH₂O⁻Na⁺ + CH₃Cl → CH₃CH₂OCH₃ + NaCl.
Diagram: Draw CH₃CH₂O⁻ attacking CH₃Cl from behind, Cl⁻ leaving, forming the ether.
Key Points: Best with primary halides to avoid elimination.
19. Ether Substitution
Introduction: Ethers cleave with concentrated acids (like HI) to form alcohols and alkyl halides.
Mechanism: Protonation of O, followed by halide attack. Example: CH₃CH₂OCH₂CH₃ + HI → CH₃CH₂OH + CH₃CH₂I.
Diagram: Show ether with H⁺ on O, I⁻ breaking one C-O bond, forming ROH and RI.
Key Points: With excess HI, both products can be halides; depends on ether type.
20. Aldehydes, Ketones, and Carboxylic Acids
Introduction: These are carbonyl compounds: aldehydes (RCHO), ketones (RCOR’), and carboxylic acids (RCOOH) differ in structure and reactivity.
Reactions:
- Aldehydes: Oxidation (RCHO → RCOOH).
- Ketones: Resistant to oxidation.
- Carboxylic acids: Esterification (RCOOH + R’OH → RCOOR’).
Diagram: Draw RCHO with C=O and H, RCOR’ with C=O between carbons, RCOOH with C=O and OH.
Key Points: Aldehydes reduce Tollens’/Fehling’s; ketones don’t; acids are acidic.
21. Rosenmund Reaction
Introduction: Reduces acid chlorides (RCOCl) to aldehydes using H₂ and Pd catalyst.
Mechanism: Selective hydrogenation. Example: CH₃COCl + H₂ (Pd/BaSO₄) → CH₃CHO + HCl.
Diagram: Show CH₃COCl with H₂ attacking, Cl leaving, forming CH₃CHO.
Key Points: BaSO₄ poisons Pd to stop at aldehyde, not alcohol.
22. Stephen Reaction
Introduction: Converts nitriles (RCN) to aldehydes using SnCl₂ and HCl, followed by hydrolysis.
Mechanism: Forms an imine salt, hydrolyzed to RCHO. Example: CH₃CN → CH₃CHO.
Diagram: Draw CH₃CN, SnCl₂/HCl reducing to CH₃CH=NH₂⁺Cl⁻, then H₂O forming CH₃CHO.
Key Points: Alternative to hydration of alkynes for aldehydes.
23. Etard Reaction
Introduction: Oxidizes toluene derivatives to aldehydes using chromyl chloride (CrO₂Cl₂).
Mechanism: Forms a complex, hydrolyzed to RCHO. Example: C₆H₅CH₃ → C₆H₅CHO.
Diagram: Show toluene with CrO₂Cl₂ adding to CH₃, then H₂O forming -CHO.
Key Points: Specific for benzylic methyl groups.
24. Gattermann-Koch Reaction
Introduction: Adds a formyl group (-CHO) to benzene using CO, HCl, and AlCl₃/CuCl.
Mechanism: CO + HCl form HCO⁺ electrophile. Example: C₆H₆ → C₆H₅CHO.
Diagram: Draw benzene, HCO⁺ attacking, H⁺ leaving to form benzaldehyde.
Key Points: Like Friedel-Crafts but for aldehydes.
25. Clemmensen Reduction
Introduction: Reduces ketones/aldehydes to hydrocarbons using Zn(Hg) and HCl.
Mechanism: Removes C=O via electron transfer. Example: CH₃COCH₃ → CH₃CH₂CH₃.
Diagram: Show CH₃COCH₃, Zn(Hg) stripping O, forming CH₃CH₂CH₃.
Key Points: Acidic conditions; good for acid-stable compounds.
26. Wolff-Kishner Reduction
Introduction: Reduces carbonyls to hydrocarbons using hydrazine (N₂H₄) and base (KOH).
Mechanism: Forms hydrazone, then loses N₂. Example: CH₃COCH₃ → CH₃CH₂CH₃.
Diagram: Draw CH₃COCH₃ + N₂H₄ → hydrazone, then N₂ gas leaving.
Key Points: Basic conditions; complements Clemmensen.
27. Aldol Condensation Reaction
Introduction: Two aldehydes/ketones with α-H combine to form a β-hydroxy carbonyl compound.
Mechanism: Base forms enolate, attacks another C=O. Example: 2CH₃CHO → CH₃CH(OH)CH₂CHO.
Diagram: Show CH₃CHO, enolate CH₂CHO⁻ attacking, forming aldol with -OH and -CHO.
Key Points: Dehydration often follows, forming α,β-unsaturated compounds.
28. Cross Aldol Condensation Reaction
Introduction: Aldol between two different carbonyls, one often lacking α-H (e.g., benzaldehyde).
Mechanism: Similar to aldol. Example: CH₃CHO + C₆H₅CHO → C₆H₵CH=CHCHO.
Diagram: Draw CH₃CHO enolate attacking C₆H₅CHO, dehydrating to a double bond.
Key Points: Controlled to avoid multiple products.
29. Cannizzaro Reaction
Introduction: Aldehydes without α-H disproportionate to alcohol and acid with strong base.
Mechanism: One RCHO reduces, one oxidizes. Example: 2C₆H₅CHO → C₆H₅CH₂OH + C₆H₅COOH.
Diagram: Show two benzaldehydes, OH⁻ transferring H⁻, forming alcohol and acid.
Key Points: Specific to non-enolizable aldehydes.
30. Decarboxylation Reaction
Introduction: Removes -COOH as CO₂, often from β-keto acids or salts with soda lime.
Mechanism: Heat-driven loss of CO₂. Example: CH₃COCH₂COOH → CH₃COCH₃ + CO₂.
Diagram: Draw CH₃COCH₂COOH, CO₂ bubbling off, leaving acetone.
Key Points: Simplifies molecules; soda lime aids aromatic acids.
Let’s finish off the list with the remaining reactions (31-38). I’ll keep the same Class 12-friendly style—clear explanations, simplified mechanisms, examples, and diagram descriptions you can visualize or sketch. Here we go!
31. HVZ Reaction (Hell-Volhard-Zelinsky Reaction)
Introduction: This reaction halogenates the α-carbon of carboxylic acids using a halogen (like Br₂) and phosphorus (P or PBr₃).
Mechanism: Forms an acyl halide intermediate, then α-H is replaced by halogen. Example: CH₃COOH + Br₂ (PBr₃) → CH₂BrCOOH + HBr.
Diagram: Draw CH₃COOH, show Br₂/PBr₃ converting -OH to -Br temporarily, then Br attaching to CH₂.
Key Points: Needs α-H; useful for further synthesis like amino acids.
32. Hoffmann Bromamide Degradation
Introduction: Converts primary amides (RCONH₂) to primary amines (RNH₂) with one less carbon using Br₂ and NaOH.
Mechanism: Forms an isocyanate intermediate, losing CO₂. Example: CH₃CONH₂ + Br₂ + 4NaOH → CH₃NH₂ + Na₂CO₃ + 2NaBr + 2H₂O.
Diagram: Show CH₃CONH₂, Br₂ adding to N, rearrangement to CH₃N=C=O, then hydrolysis to CH₃NH₂.
Key Points: Shortens carbon chain; specific to primary amides.
33. Gabriel Phthalimide Synthesis Reaction
Introduction: Prepares primary aliphatic amines from phthalimide and alkyl halides, avoiding over-alkylation.
Mechanism: Phthalimide reacts with base, then R-X, hydrolyzed to RNH₂. Example: Phthalimide + CH₃CH₂Cl → CH₃CH₂NH₂.
Diagram: Draw phthalimide (two C=O groups on a benzene ring), N⁻ attacking CH₃CH₂Cl, then OH⁻ opening it to CH₃CH₂NH₂.
Key Points: Clean method for 1° amines; no 2° or 3° side products.
34. Carbylamine Reaction
Introduction: Tests for primary amines by forming foul-smelling isocyanides (RNC) with CHCl₃ and KOH.
Mechanism: Amine reacts with dichlorocarbene (:CCl₂) from CHCl₃. Example: CH₃NH₂ + CHCl₃ + 3KOH → CH₃NC + 3KCl + 3H₂O.
Diagram: Show CH₃NH₂, :CCl₂ (from CHCl₃/KOH) attaching, losing Cl⁻ to form CH₃N≡C.
Key Points: Diagnostic for 1° amines; isocyanides stink like rotten fish!
35. Nitration (With Nitration)
Introduction: Adds a nitro group (-NO₂) to aromatic rings using HNO₃ and H₂SO₄.
Mechanism: H₂SO₄ protonates HNO₃, forming NO₂⁺ electrophile. Example: C₆H₆ + HNO₃ → C₆H₅NO₂ + H₂O.
Diagram: Draw benzene, NO₂⁺ attacking, forming a sigma complex (ring with + charge), then H⁺ leaving.
Key Points: H₂SO₄ activates HNO₃; directs ortho/para or meta based on substituents.
36. Diazotization Reaction
Introduction: Converts primary aromatic amines (ArNH₂) to diazonium salts (ArN₂⁺) using NaNO₂ and HCl at 0-5°C.
Mechanism: HNO₂ (from NaNO₂ + HCl) reacts with amine to form ArN₂⁺. Example: C₆H₅NH₂ + NaNO₂ + 2HCl → C₆H₅N₂Cl + 2H₂O.
Diagram: Show C₆H₅NH₂, HNO₂ adding N, forming C₆H₅N≡N⁺Cl⁻ with N₂ gas-like structure.
Key Points: Cold conditions critical; diazonium salts are versatile intermediates.
37. Coupling Reaction
Introduction: Diazonium salts react with phenols or aromatic amines to form brightly colored azo compounds (-N=N-).
Mechanism: ArN₂⁺ attacks electron-rich ring. Example: C₆H₅N₂Cl + C₆H₅OH → C₆H₅N=NC₆H₅OH + HCl.
Diagram: Draw C₆H₅N₂⁺, attacking phenol at para position, forming an orange azo dye with -N=N- linkage.
Key Points: Used in dye industry; occurs in basic/acidic medium depending on partner.
38. Hunsdiecker Reaction
Introduction: Converts carboxylic acid silver salts (RCOOAg) to alkyl halides (RX) with one less carbon using Br₂.
Mechanism: Decarboxylation via radical intermediate. Example: CH₃COOAg + Br₂ → CH₃Br + CO₂ + AgBr.
Diagram: Show CH₃COOAg, Br₂ breaking off CO₂, forming CH₃• and Br• combining into CH₃Br.
Key Points: Loses one carbon; works best with Br₂ or I₂.
Conclusion:
Organic chemistry’s naming reactions no longer need to feel overwhelming! With this guide, you’ve explored 40+ essential reactions—their mechanisms, real-world applications, and tricks to remember them. Whether it’s the Rosenmund reduction for aldehydes or the Gabriel synthesis for amines, each topic is designed to boost your confidence and clarity. Use this resource to decode reaction pathways, tackle numericals, and sharpen your problem-solving skills. Remember, consistent practice and visualizing mechanisms (like SN2 backside attacks or electrophilic substitution) are keys to success. Now go crush those exams and embrace the magic of molecules!
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