HALOALKANES AND HALOARENES - SHORT
BOARD NOTES
1. Classification:
Haloalkanes (R-X) and Haloarenes (Ar-X).
Primary (1°), Secondary (2°), Tertiary (3°).
2. Nature of C-X Bond:
Polar bond. Reactivity order: RI > RBr > RCl > RF.
Bond strength: C-F > C-Cl > C-Br > C-I.
3. Preparation:
From alcohols (ROH + HX → RX + H2O).
From alkanes (Free radical halogenation).
From alkenes (Markovnikov & Anti-Markovnikov rule).
From benzene (Electrophilic substitution).
Sandmeyer reaction from diazonium salts.
4. Physical Properties:
Boiling point increases with molecular mass.
Insoluble in water, soluble in organic solvents.
5. Chemical Reactions of Haloalkanes:
SN1: Two-step, carbocation intermediate, 3° > 2° > 1°.
SN2: One-step, backside attack, 1° > 2° > 3°.
Elimination (Alcoholic KOH) follows Zaitsev rule.
Wurtz reaction: 2R-X + 2Na → R-R + 2NaX.
6. Haloarenes:
Less reactive due to resonance and partial double bond character.
Undergo electrophilic substitution (ortho-para directing).
BOARD NOTES
1. Classification:
Haloalkanes (R-X) and Haloarenes (Ar-X).
Primary (1°), Secondary (2°), Tertiary (3°).
2. Nature of C-X Bond:
Polar bond. Reactivity order: RI > RBr > RCl > RF.
Bond strength: C-F > C-Cl > C-Br > C-I.
3. Preparation:
From alcohols (ROH + HX → RX + H2O).
From alkanes (Free radical halogenation).
From alkenes (Markovnikov & Anti-Markovnikov rule).
From benzene (Electrophilic substitution).
Sandmeyer reaction from diazonium salts.
4. Physical Properties:
Boiling point increases with molecular mass.
Insoluble in water, soluble in organic solvents.
5. Chemical Reactions of Haloalkanes:
SN1: Two-step, carbocation intermediate, 3° > 2° > 1°.
SN2: One-step, backside attack, 1° > 2° > 3°.
Elimination (Alcoholic KOH) follows Zaitsev rule.
Wurtz reaction: 2R-X + 2Na → R-R + 2NaX.
6. Haloarenes:
Less reactive due to resonance and partial double bond character.
Undergo electrophilic substitution (ortho-para directing).
