Mindmap ✨

Topic: HALOALKANES & HALOARENES


1️⃣ #HALOALKANES
✔️ Alkanes in which H is replaced by halogen (F, Cl, Br, I)
✔️ General formula → R–X
📌 X = halogen atom
Example:
✔️ CH₃Cl (Methyl chloride)


2️⃣ #HALOARENES
✔️ Halogen directly attached to benzene ring
📌 Example:
✔️ Chlorobenzene
Important difference:
✔️ Haloarenes less reactive than haloalkanes


3️⃣ #CLASSIFICATION ⭐⭐⭐
✔️ Primary (1°) → RCH₂X
✔️ Secondary (2°) → R₂CHX
✔️ Tertiary (3°) → R₃CX
📌 Reactivity in substitution:
✔️ 3° > 2° > 1°


4️⃣ #PREPARATIONOFHALOALKANES ⭐⭐
📌 From alcohols
ROH + HX → RX + H₂O
Reagents:
✔️ HCl + ZnCl₂ (Lucas reagent)
✔️ PCl₅
✔️ SOCl₂


5️⃣ #HALOGENATIONOFALKANES
✔️ Alkane + halogen → Haloalkane
Example:
CH₄ + Cl₂ → CH₃Cl + HCl
Condition:
✔️ UV light / sunlight


6️⃣ #NUCLEOPHILICSUBSTITUTION ⭐⭐⭐
✔️ Most important reaction of haloalkanes
Example:
R–Cl + OH⁻ → R–OH + Cl⁻
📌 Nucleophile replaces halogen
Common nucleophiles:
✔️ OH⁻
✔️ CN⁻
✔️ NH₃

.7️⃣ #SN1REACTION ⭐⭐⭐
✔️ Two step mechanism
✔️ Carbocation intermediate
Rate depends on:
✔️ Concentration of substrate
📌 Favoured by:
✔️ 3° haloalkanes


8️⃣ #SN2REACTION ⭐⭐⭐
✔️ One step mechanism
✔️ Backside attack
Rate depends on:
✔️ Substrate + nucleophile
📌 Favoured by:
✔️ 1° haloalkanes


9️⃣ #ELIMINATIONREACTION ⭐⭐
✔️ Haloalkane → Alkene
Example:
R–CH₂–CH₂Cl + alc. KOH → Alkene
📌 Called β-elimination


🔟 #WURTZREACTION ⭐⭐
✔️ Haloalkane + Na (dry ether)
Reaction:
2R–X + 2Na → R–R + 2NaX
Product:
✔️ Higher alkane


1️⃣1️⃣ #HALOARENESREACTIONS ⭐⭐
✔️ Less reactive in substitution
Reason:
✔️ Resonance stabilization
✔️ Partial double bond character


1️⃣2️⃣ #NEETIMPORTANTPOINTS
✔️ Haloalkanes show nucleophilic substitution
✔️ SN1 → carbocation mechanism
✔️ SN2 → backside attack
✔️ Haloarenes less reactive


1️⃣3️⃣ #ONELINEREVISION
✔️ Haloalkane = R–X
✔️ SN1 → 3° favoured
✔️ SN2 → 1° favoured
✔️ Alcohol → Haloalkane (Lucas reagent)
✔️ Haloarene less reactive due to resonance

1️⃣ #HALOARENES
✔️ Aromatic compounds in which halogen attached directly to benzene ring
✔️ General formula → Ar–X
📌 Example:
✔️ Chlorobenzene
✔️ Bromobenzene


2️⃣ #STRUCTURE ⭐⭐⭐
✔️ Halogen attached to sp² carbon of benzene ring
✔️ C–X bond shorter than haloalkanes
📌 Reason:
✔️ Resonance gives partial double bond character


3️⃣ #LOWREACTIVITYOFHALOARENES ⭐⭐⭐
✔️ Haloarenes less reactive in nucleophilic substitution
Reasons:
✔️ Resonance stabilization
✔️ Partial double bond character of C–X bond
✔️ sp² carbon stronger bond than sp³


4️⃣ #PREPARATIONOFHALOARENES ⭐⭐
✔️ From benzene by electrophilic substitution
Reaction:
Benzene + Cl₂ → Chlorobenzene
Catalyst:
✔️ FeCl₃ / AlCl₃


5️⃣ #DOWPROCESS ⭐⭐⭐
✔️ Preparation of phenol from chlorobenzene
Conditions:
✔️ NaOH
✔️ 623 K
✔️ 300 atm
Reaction:
Chlorobenzene → Phenol


6️⃣ #NUCLEOPHILICSUBSTITUTION
Occurs only under drastic conditions
Example:
Chlorobenzene + NaOH → Phenol
📌 Requires high temperature & pressure


7️⃣ #ELECTROPHILICSUBSTITUTION ⭐⭐⭐
Haloarenes undergo electrophilic substitution easily.
Examples:
✔️ Nitration
✔️ Halogenation
✔️ Sulphonation
📌 Halogen acts as:
✔️ Deactivating group
✔️ Ortho / para directing


8️⃣ #DIRECTINGEFFECT ⭐⭐⭐
✔️ Halogens deactivate ring
✔️ But direct substitution to ortho & para positions
Reason:
✔️ Resonance donation


9️⃣ #NEETIMPORTANTPOINTS
✔️ Haloarenes less reactive than haloalkanes
✔️ Halogen is deactivating but o,p-directing
✔️ Dow process used for phenol formation


🔟 #ONELINEREVISION
✔️ Haloarene = Ar–X
✔️ C–X bond strong due to resonance
✔️ Electrophilic substitution occurs
✔️ Halogen = deactivating but o,p-directing

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