Hala Alkaan aur Hala Aryans

Swagat aur Parichay

Lecture: Mind Map Series
Topic: Haloalkanes and Haloarenes
Agenda: Quick revision of reactions, methods of preparation, and chemical properties, followed by questions.

From Alcohols: Using HX
- Reaction: R-CH2-OH + HX → R-CH2-X
- Primary alcohols: Use conc. HCl + ZnCl2 (Lucas reagent)
- Lucas Test: Distinguishing primary, secondary, and tertiary alcohols based on turbidity formation times.
From Alkenes: Using HX
- Reaction: Alkene + HX → Carbocation rearrangement (if possible) → Product
- Stability of carbocation affects the rate.
From Alkanes: Halogenation (Free radical mechanism)
- Reaction: Alkane + X2 (Sunlight/UV light) → Alkyl halide
From Alkenes: Using X2 in CCl4/NBS
- Reaction: Alkene + X2 → Vicinal dihalide (anti addition)
- With water (Bromine water test) forms halohydrin.
Swart's Reaction:
- Reaction: R-X + AgF/CoF2/Hg2F2 → R-F

Nucleophilic Substitution Reaction (SN1 and SN2)
- SN1: 2-step (formation of carbocation)
  - Rate dependent on carbocation stability
  - Partial racemization occurs.
- SN2: 1-step (backside attack)
  - Gives 100% inversion of configuration (Walden inversion)
  - Rate dependent on steric hindrance and strength of nucleophile.
Elimination Reactions (E1 and E2)
- E1: 2-step (carbocation intermediate)
  - Favors Zaitsev product.
- E2: 1-step (anti-periplanar transition state)
  - Zaitsev product (more substituted alkene is major).
Elimination-Addition Mechanism for Benzene Derivatives (SNI)
- Involves elimination followed by addition.

Wurtz Reaction:
- Reaction: Alkyl halides + Na (Dry ether) → Alkanes
Grignard Reagent Formation:
- Reaction: R-X + Mg (Dry ether) → RMgX
- Precaution: Must avoid moisture.

Electrophilic Substitution Reactions
- Bromination/Chlorination: Benzene + X2 (Anhyd. AlCl3/FeX3)
- Nitration: Benzene + HNO3 (Conc. H2SO4)
- Sulfonation: Benzene + SO3 (Oleum)
- Friedel-Crafts Alkylation: Benzene + RCl (Anhyd. AlCl3)
Sandmeyer Reaction:
- Reaction: Aniline → Diazonium salt → Haloarene via CuCl/CuBr
Gattermann Reaction:
- Similar to Sandmeyer but with different reagents.

Generally less reactive in nucleophilic substitutions due to resonance stabilization.
Special conditions required for nucleophilic aromatic substitution (SNAr).
Example: Dow's Process for conversion of chlorobenzene to phenol under high temperature and pressure.

Benzyne Mechanism: Involves elimination followed by addition.
Fittig Reaction: For diaryl compounds preparation using sodium in the dry ether.
Kolbe's Reaction and Reimer-Tiemann Reaction: Specific to phenol derivatives.

The lecture provided comprehensive coverage and quick revision of key concepts related to Haloalkanes and Haloarenes.
Interactive questions at the end to solidify understanding and application of concepts.

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