CLASS 12 ORGANIC CHEMISTRY
Haloalkanes & Haloarenes
Quick Revision Notes & Key Reaction Mechanisms
1. Important Definitions & Concepts
• Haloalkanes (Alkyl Halides): Jab kisi Aliphatic hydrocarbon (R–H) me se Hydrogen atom ko Halogen (X
= F, Cl, Br, I) se replace kiya jata hai.
General Formula: R–X
• Haloarenes (Aryl Halides): Jab Aromatic ring (Benzene) me se Hydrogen atom ko Halogen se replace
kiya jata hai.
General Formula: Ar–X
• Nature of C–X Bond: Carbon aur Halogen ke beech ka bond polar hota hai kyunki Halogen ki
electronegativity Carbon se zyada hoti hai (Cδ+–Xδ−).
2. Preparation Methods
A. Haloalkanes:
1. From Alcohols:
• R–OH + HCl ⟶ZnCl2 R–Cl + H2O (Lucas Test)
• 3R–OH + PCl3 ⟶ 3R–Cl + H3PO3
• R–OH + SOCl2 ⟶ R–Cl + SO2↑ + HCl↑ (Best method: gaseous products escape)
2. Halogen Exchange Reactions:
• Finkelstein Reaction: R–X + NaI ⟶Dry Acetone R–I + NaX (jahan X = Cl, Br)
• Swarts Reaction: R–Br + AgF ⟶ R–F + AgBr (Fluorides banane ke liye)
B. Haloarenes:
1. Sandmeyer’s Reaction:
Aniline ⟶NaNO2 + HCl, 0–5°C Benzene Diazonium Chloride ⟶Cu2Cl2 / HCl Chlorobenzene
Class 12 Organic Chemistry Revision Notes Page 1 of 2
Haloalkanes & Haloarenes
Quick Revision Notes & Key Reaction Mechanisms
1. Important Definitions & Concepts
• Haloalkanes (Alkyl Halides): Jab kisi Aliphatic hydrocarbon (R–H) me se Hydrogen atom ko Halogen (X
= F, Cl, Br, I) se replace kiya jata hai.
General Formula: R–X
• Haloarenes (Aryl Halides): Jab Aromatic ring (Benzene) me se Hydrogen atom ko Halogen se replace
kiya jata hai.
General Formula: Ar–X
• Nature of C–X Bond: Carbon aur Halogen ke beech ka bond polar hota hai kyunki Halogen ki
electronegativity Carbon se zyada hoti hai (Cδ+–Xδ−).
2. Preparation Methods
A. Haloalkanes:
1. From Alcohols:
• R–OH + HCl ⟶ZnCl2 R–Cl + H2O (Lucas Test)
• 3R–OH + PCl3 ⟶ 3R–Cl + H3PO3
• R–OH + SOCl2 ⟶ R–Cl + SO2↑ + HCl↑ (Best method: gaseous products escape)
2. Halogen Exchange Reactions:
• Finkelstein Reaction: R–X + NaI ⟶Dry Acetone R–I + NaX (jahan X = Cl, Br)
• Swarts Reaction: R–Br + AgF ⟶ R–F + AgBr (Fluorides banane ke liye)
B. Haloarenes:
1. Sandmeyer’s Reaction:
Aniline ⟶NaNO2 + HCl, 0–5°C Benzene Diazonium Chloride ⟶Cu2Cl2 / HCl Chlorobenzene
Class 12 Organic Chemistry Revision Notes Page 1 of 2
