Page 1
Haloalkanes and Haloarenes Cheat Sheet
(EduRev)
Introduction and Classification
Key Concepts
? Haloalkanes: R–X (X = F, Cl, Br, I), classified as 1°, 2°, 3° based on carbon substitution.
? Haloarenes: Ar–X, halogen on aromatic ring.
? Nomenclature: IUPAC, e.g., CH
3
CH
2
Br ? 1-bromoethane, C
6
H
5
Cl ? chlorobenzene.
Physical Properties
Key Concepts
? Boiling Points: Increase with molecular weight (I > Br > Cl > F).
? Solubility: Insoluble in water, soluble in organic solvents.
? Dipole Moment: Haloalkanes > haloarenes due to resonance in Ar–X.
Preparation Methods
Haloalkanes
? From alcohols: R–OH + HX ? R–X + H
2
O (ZnCl
2
, 1°/2°).
? From alkenes: R–CH=CH
2
+ HX ? R–CHX–CH
3
(Markovnikov).
? Halogen exchange: R–Br + NaI ? R–I + NaBr (Finkelstein, acetone).
Page 2
Haloalkanes and Haloarenes Cheat Sheet
(EduRev)
Introduction and Classification
Key Concepts
? Haloalkanes: R–X (X = F, Cl, Br, I), classified as 1°, 2°, 3° based on carbon substitution.
? Haloarenes: Ar–X, halogen on aromatic ring.
? Nomenclature: IUPAC, e.g., CH
3
CH
2
Br ? 1-bromoethane, C
6
H
5
Cl ? chlorobenzene.
Physical Properties
Key Concepts
? Boiling Points: Increase with molecular weight (I > Br > Cl > F).
? Solubility: Insoluble in water, soluble in organic solvents.
? Dipole Moment: Haloalkanes > haloarenes due to resonance in Ar–X.
Preparation Methods
Haloalkanes
? From alcohols: R–OH + HX ? R–X + H
2
O (ZnCl
2
, 1°/2°).
? From alkenes: R–CH=CH
2
+ HX ? R–CHX–CH
3
(Markovnikov).
? Halogen exchange: R–Br + NaI ? R–I + NaBr (Finkelstein, acetone).
Haloarenes
? Electrophilic substitution: C
6
H
6
+ Cl
2
? C
6
H
5
Cl (FeCl
3
).
? Sandmeyer’s: Ar–N
2
+
Cl
-
+ CuCl ? Ar–Cl + N
2
.
Chemical Reactions of Haloalkanes
Nucleophilic Substitution
? S
N
2: 1°, concerted, inversion, e.g., CH
3
Br + OH
-
? CH
3
OH + Br
-
.
? S
N
1: 3°, carbocation, racemization, e.g., (CH
3
)
3
CBr ? (CH
3
)
3
C
+
? (CH
3
)
3
COH.
Elimination
? E2: 2°/3°, concerted, Zaitsev’s rule, e.g., CH
3
CHBrCH
3
+ OH
-
? CH
3
CH=CH
2
.
? E1: 3°, carbocation, e.g., (CH
3
)
3
CBr ? (CH
3
)
2
C=CH
2
.
Reactions with Metals
? Grignard: R–X + Mg ? R–MgX (dry ether).
? Wurtz: 2R–X + 2Na ? R–R + 2NaX.
Chemical Reactions of Haloarenes
Key Reactions
? Electrophilic Substitution: Halogens o,p-directing, deactivating, e.g., C
6
H
5
Cl + HNO
3
?
o/p-C
6
H
4
ClNO
2
.
? Nucleophilic Substitution: Dow’s process, C
6
H
5
Cl + NaOH ? C
6
H
5
OH (350°C, 300
atm).
? Benzyne Mechanism: C
6
H
5
Cl + NH
2
-
? C
6
H
5
NH
2
.
Page 3
Haloalkanes and Haloarenes Cheat Sheet
(EduRev)
Introduction and Classification
Key Concepts
? Haloalkanes: R–X (X = F, Cl, Br, I), classified as 1°, 2°, 3° based on carbon substitution.
? Haloarenes: Ar–X, halogen on aromatic ring.
? Nomenclature: IUPAC, e.g., CH
3
CH
2
Br ? 1-bromoethane, C
6
H
5
Cl ? chlorobenzene.
Physical Properties
Key Concepts
? Boiling Points: Increase with molecular weight (I > Br > Cl > F).
? Solubility: Insoluble in water, soluble in organic solvents.
? Dipole Moment: Haloalkanes > haloarenes due to resonance in Ar–X.
Preparation Methods
Haloalkanes
? From alcohols: R–OH + HX ? R–X + H
2
O (ZnCl
2
, 1°/2°).
? From alkenes: R–CH=CH
2
+ HX ? R–CHX–CH
3
(Markovnikov).
? Halogen exchange: R–Br + NaI ? R–I + NaBr (Finkelstein, acetone).
Haloarenes
? Electrophilic substitution: C
6
H
6
+ Cl
2
? C
6
H
5
Cl (FeCl
3
).
? Sandmeyer’s: Ar–N
2
+
Cl
-
+ CuCl ? Ar–Cl + N
2
.
Chemical Reactions of Haloalkanes
Nucleophilic Substitution
? S
N
2: 1°, concerted, inversion, e.g., CH
3
Br + OH
-
? CH
3
OH + Br
-
.
? S
N
1: 3°, carbocation, racemization, e.g., (CH
3
)
3
CBr ? (CH
3
)
3
C
+
? (CH
3
)
3
COH.
Elimination
? E2: 2°/3°, concerted, Zaitsev’s rule, e.g., CH
3
CHBrCH
3
+ OH
-
? CH
3
CH=CH
2
.
? E1: 3°, carbocation, e.g., (CH
3
)
3
CBr ? (CH
3
)
2
C=CH
2
.
Reactions with Metals
? Grignard: R–X + Mg ? R–MgX (dry ether).
? Wurtz: 2R–X + 2Na ? R–R + 2NaX.
Chemical Reactions of Haloarenes
Key Reactions
? Electrophilic Substitution: Halogens o,p-directing, deactivating, e.g., C
6
H
5
Cl + HNO
3
?
o/p-C
6
H
4
ClNO
2
.
? Nucleophilic Substitution: Dow’s process, C
6
H
5
Cl + NaOH ? C
6
H
5
OH (350°C, 300
atm).
? Benzyne Mechanism: C
6
H
5
Cl + NH
2
-
? C
6
H
5
NH
2
.
? Wurtz-Fittig: Ar–X + R–X + 2Na ? Ar–R.
Reaction Mechanisms
Haloalkanes
? S
N
2: Nucleophile attacks C, X leaves, transition state, inversion.
? S
N
1: X leaves, forms carbocation, nucleophile attacks, racemization.
? E2: Base abstracts ß-H, X leaves, alkene forms, anti-elimination.
? E1: X leaves, carbocation forms, base abstracts ß-H.
Haloarenes
? Benzyne: Base abstracts H, X leaves, forms benzyne, nucleophile adds.
? Electrophilic Substitution: Electrophile attacks ring, H leaves, forms substituted
product.
Applications and Environmental Impact
Key Concepts
? Uses: Solvents (CHCl
3
, CCl
4
), refrigerants (CFCs), pesticides (DDT).
? Environmental: CFCs deplete ozone, DDT is toxic and persistent.
Stereochemistry
Key Concepts
? Chirality: Haloalkanes with chiral carbon (e.g., CH
3
CHBrCH
2
CH
3
) are optically active.
? S
N
2: Inversion of configuration.
Page 4
Haloalkanes and Haloarenes Cheat Sheet
(EduRev)
Introduction and Classification
Key Concepts
? Haloalkanes: R–X (X = F, Cl, Br, I), classified as 1°, 2°, 3° based on carbon substitution.
? Haloarenes: Ar–X, halogen on aromatic ring.
? Nomenclature: IUPAC, e.g., CH
3
CH
2
Br ? 1-bromoethane, C
6
H
5
Cl ? chlorobenzene.
Physical Properties
Key Concepts
? Boiling Points: Increase with molecular weight (I > Br > Cl > F).
? Solubility: Insoluble in water, soluble in organic solvents.
? Dipole Moment: Haloalkanes > haloarenes due to resonance in Ar–X.
Preparation Methods
Haloalkanes
? From alcohols: R–OH + HX ? R–X + H
2
O (ZnCl
2
, 1°/2°).
? From alkenes: R–CH=CH
2
+ HX ? R–CHX–CH
3
(Markovnikov).
? Halogen exchange: R–Br + NaI ? R–I + NaBr (Finkelstein, acetone).
Haloarenes
? Electrophilic substitution: C
6
H
6
+ Cl
2
? C
6
H
5
Cl (FeCl
3
).
? Sandmeyer’s: Ar–N
2
+
Cl
-
+ CuCl ? Ar–Cl + N
2
.
Chemical Reactions of Haloalkanes
Nucleophilic Substitution
? S
N
2: 1°, concerted, inversion, e.g., CH
3
Br + OH
-
? CH
3
OH + Br
-
.
? S
N
1: 3°, carbocation, racemization, e.g., (CH
3
)
3
CBr ? (CH
3
)
3
C
+
? (CH
3
)
3
COH.
Elimination
? E2: 2°/3°, concerted, Zaitsev’s rule, e.g., CH
3
CHBrCH
3
+ OH
-
? CH
3
CH=CH
2
.
? E1: 3°, carbocation, e.g., (CH
3
)
3
CBr ? (CH
3
)
2
C=CH
2
.
Reactions with Metals
? Grignard: R–X + Mg ? R–MgX (dry ether).
? Wurtz: 2R–X + 2Na ? R–R + 2NaX.
Chemical Reactions of Haloarenes
Key Reactions
? Electrophilic Substitution: Halogens o,p-directing, deactivating, e.g., C
6
H
5
Cl + HNO
3
?
o/p-C
6
H
4
ClNO
2
.
? Nucleophilic Substitution: Dow’s process, C
6
H
5
Cl + NaOH ? C
6
H
5
OH (350°C, 300
atm).
? Benzyne Mechanism: C
6
H
5
Cl + NH
2
-
? C
6
H
5
NH
2
.
? Wurtz-Fittig: Ar–X + R–X + 2Na ? Ar–R.
Reaction Mechanisms
Haloalkanes
? S
N
2: Nucleophile attacks C, X leaves, transition state, inversion.
? S
N
1: X leaves, forms carbocation, nucleophile attacks, racemization.
? E2: Base abstracts ß-H, X leaves, alkene forms, anti-elimination.
? E1: X leaves, carbocation forms, base abstracts ß-H.
Haloarenes
? Benzyne: Base abstracts H, X leaves, forms benzyne, nucleophile adds.
? Electrophilic Substitution: Electrophile attacks ring, H leaves, forms substituted
product.
Applications and Environmental Impact
Key Concepts
? Uses: Solvents (CHCl
3
, CCl
4
), refrigerants (CFCs), pesticides (DDT).
? Environmental: CFCs deplete ozone, DDT is toxic and persistent.
Stereochemistry
Key Concepts
? Chirality: Haloalkanes with chiral carbon (e.g., CH
3
CHBrCH
2
CH
3
) are optically active.
? S
N
2: Inversion of configuration.
? S
N
1: Racemization due to planar carbocation.
Problem-Solving Tactics
? Identify substrate type (1°, 2°, 3°, alkyl vs. aryl) to predict S
N
1/S
N
2 or E1/E2.
? Check nucleophile strength and solvent (polar protic ? S
N
1/E1, polar aprotic ? S
N
2/E2).
? Use Zaitsev’s rule for elimination products.
? Consider resonance in haloarenes for low reactivity.
? Check chirality for stereochemical outcomes.
Reaction Table
Reaction Type Reactants Reagents/Conditio
ns
Products
Haloalkane Prep R–OH HX, ZnCl
2
R–X + H
2
O
Haloalkane Prep R–CH=CH
2
HX R–CHX–CH
3
Finkelstein R–Br NaI, acetone R–I + NaBr
Haloarene Prep C
6
H
6
Cl
2
, FeCl
3
C
6
H
5
Cl
Page 5
Haloalkanes and Haloarenes Cheat Sheet
(EduRev)
Introduction and Classification
Key Concepts
? Haloalkanes: R–X (X = F, Cl, Br, I), classified as 1°, 2°, 3° based on carbon substitution.
? Haloarenes: Ar–X, halogen on aromatic ring.
? Nomenclature: IUPAC, e.g., CH
3
CH
2
Br ? 1-bromoethane, C
6
H
5
Cl ? chlorobenzene.
Physical Properties
Key Concepts
? Boiling Points: Increase with molecular weight (I > Br > Cl > F).
? Solubility: Insoluble in water, soluble in organic solvents.
? Dipole Moment: Haloalkanes > haloarenes due to resonance in Ar–X.
Preparation Methods
Haloalkanes
? From alcohols: R–OH + HX ? R–X + H
2
O (ZnCl
2
, 1°/2°).
? From alkenes: R–CH=CH
2
+ HX ? R–CHX–CH
3
(Markovnikov).
? Halogen exchange: R–Br + NaI ? R–I + NaBr (Finkelstein, acetone).
Haloarenes
? Electrophilic substitution: C
6
H
6
+ Cl
2
? C
6
H
5
Cl (FeCl
3
).
? Sandmeyer’s: Ar–N
2
+
Cl
-
+ CuCl ? Ar–Cl + N
2
.
Chemical Reactions of Haloalkanes
Nucleophilic Substitution
? S
N
2: 1°, concerted, inversion, e.g., CH
3
Br + OH
-
? CH
3
OH + Br
-
.
? S
N
1: 3°, carbocation, racemization, e.g., (CH
3
)
3
CBr ? (CH
3
)
3
C
+
? (CH
3
)
3
COH.
Elimination
? E2: 2°/3°, concerted, Zaitsev’s rule, e.g., CH
3
CHBrCH
3
+ OH
-
? CH
3
CH=CH
2
.
? E1: 3°, carbocation, e.g., (CH
3
)
3
CBr ? (CH
3
)
2
C=CH
2
.
Reactions with Metals
? Grignard: R–X + Mg ? R–MgX (dry ether).
? Wurtz: 2R–X + 2Na ? R–R + 2NaX.
Chemical Reactions of Haloarenes
Key Reactions
? Electrophilic Substitution: Halogens o,p-directing, deactivating, e.g., C
6
H
5
Cl + HNO
3
?
o/p-C
6
H
4
ClNO
2
.
? Nucleophilic Substitution: Dow’s process, C
6
H
5
Cl + NaOH ? C
6
H
5
OH (350°C, 300
atm).
? Benzyne Mechanism: C
6
H
5
Cl + NH
2
-
? C
6
H
5
NH
2
.
? Wurtz-Fittig: Ar–X + R–X + 2Na ? Ar–R.
Reaction Mechanisms
Haloalkanes
? S
N
2: Nucleophile attacks C, X leaves, transition state, inversion.
? S
N
1: X leaves, forms carbocation, nucleophile attacks, racemization.
? E2: Base abstracts ß-H, X leaves, alkene forms, anti-elimination.
? E1: X leaves, carbocation forms, base abstracts ß-H.
Haloarenes
? Benzyne: Base abstracts H, X leaves, forms benzyne, nucleophile adds.
? Electrophilic Substitution: Electrophile attacks ring, H leaves, forms substituted
product.
Applications and Environmental Impact
Key Concepts
? Uses: Solvents (CHCl
3
, CCl
4
), refrigerants (CFCs), pesticides (DDT).
? Environmental: CFCs deplete ozone, DDT is toxic and persistent.
Stereochemistry
Key Concepts
? Chirality: Haloalkanes with chiral carbon (e.g., CH
3
CHBrCH
2
CH
3
) are optically active.
? S
N
2: Inversion of configuration.
? S
N
1: Racemization due to planar carbocation.
Problem-Solving Tactics
? Identify substrate type (1°, 2°, 3°, alkyl vs. aryl) to predict S
N
1/S
N
2 or E1/E2.
? Check nucleophile strength and solvent (polar protic ? S
N
1/E1, polar aprotic ? S
N
2/E2).
? Use Zaitsev’s rule for elimination products.
? Consider resonance in haloarenes for low reactivity.
? Check chirality for stereochemical outcomes.
Reaction Table
Reaction Type Reactants Reagents/Conditio
ns
Products
Haloalkane Prep R–OH HX, ZnCl
2
R–X + H
2
O
Haloalkane Prep R–CH=CH
2
HX R–CHX–CH
3
Finkelstein R–Br NaI, acetone R–I + NaBr
Haloarene Prep C
6
H
6
Cl
2
, FeCl
3
C
6
H
5
Cl
Reaction Type Reactants Reagents/Conditio
ns
Products
Sandmeyer’s Ar–N
2
+
Cl
-
CuCl Ar–Cl + N
2
S
N
2 CH
3
Br OH
-
, polar aprotic CH
3
OH + Br
-
S
N
1 (CH
3
)
3
CBr H
2
O, polar protic (CH
3
)
3
COH
E2 CH
3
CHBrCH
3
OH
-
, heat CH
3
CH=CH
2
E1 (CH
3
)
3
CBr H
2
O, heat (CH
3
)
2
C=CH
2
Grignard R–X Mg, dry ether R–MgX
Wurtz 2R–X 2Na R–R + 2NaX
Electrophilic Sub C
6
H
5
Cl HNO
3
, H
2
SO
4
C
6
H
4
ClNO
2
Dow’s Process C
6
H
5
Cl NaOH, 350°C, 300
atm
C
6
H
5
OH
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