12C10

​

Haloalkanes & Haloarenes

Introduction

Haloalkanes

&

Haloarenes ???

Aliphatic / Aromatic Hydrocarbons

-H

+X

Haloalkanes / Haloarenes

Introduction

Aliphatic Hydrocarbons

-H

+X

Haloalkanes

(Alkyl halides)

Methane

Methyl chloride

Introduction

Aromatic Hydrocarbons

-H

+X

Haloarenes

(Aryl halides)

Why Haloalkanes & Haloarenes ??

Wide applications in industry as well as in day-to-day life :

Poly Vinyl Chloride

Chloroform

Wide applications in industry as well as in day-to-day life :

Teflon

DDT

Why Haloalkanes & Haloarenes ??

• Halothane is used as an anaesthetic during surgery

Chloroquine

Chloramphenicol

Treatment of Typhoid fever

Treatment of Malaria

• Our body produces iodine containing hormone, thyroxine, the deficiency of which causes a disease called goiter

Why Haloalkanes & Haloarenes ??

12C10.1

​

Classification, Nomenclature

& Nature of C-X bond

12C12.1 Classification, Nomenclature & Nature of C-X bond

Learning Objectives

​

Classification of Halogen containing Compounds

​

Nomenclature of Halogen containing Compounds

​

Nature of C-X bond in Halogen containing Compounds

​

12C10.1

​

CV 1

​

Classification of Halogen

containing Compounds

​

Classification

On the Basis of Number of Halogens :

Monohalogen

Compound

Dihalogen

Compound

Polyhalogen

Compound

Monohaloalkane

Dihaloalkane

Trihaloalkane

Classification

On the Basis of Number of Halogens :

Monohalogen

Compound

Dihalogen

Compound

Polyhalogen

Compound

Monohaloarene

Dihaloarene

Trihaloarene

Classification

Monohalogen Compounds

Classification

Monohalogen Compounds

Alkyl Halides

(Haloalkanes)

Allylic Halides

Benzylic Halides

Allylic carbon

Benzylic carbon

Classification

Monohalogen Compounds

Vinylic Halides

Aryl Halides

12C10.1

​

CV 2

​

Nomenclature of Halogen

containing Compounds

Nomenclature

• IUPAC Naming : Haloalkane

Ethylchloride

Methylfluoride

(n-Propylbromide)

(iso-Propyliodide)

(neo-Pentylchloride)

• Common Naming : Alkyl Halide

Common Naming

Nomenclature

• Prefix used : Halo

Chloroethane

Fluoromethane

1-Bromopropane

2-Iodopropane

1-Chloro-2,2-dimethylpropane

trans-3,4-Dichlorohex-3-ene

3

2

1

3

2

1

3

2

1

3

2

1

4

5

6

IUPAC Naming

Nomenclature

Bromobenzene

1,2-Dibromobenzene

(o-Dibromobenzene)

1,4-Dibromobenzene

(p-Dibromobenzene)

Chloroethene

(Vinyl chloride)

3-Bromopropene

(Allyl bromide)

Trichloromethane

(Chloroform)

3

2

1

4

5

6

3

2

1

4

5

6

3

2

1

12C10.1

​

PSV 1

Q.

Write IUPAC names of the following compounds :

Sol.

1

3

2

3

2

1

4

5

3-Bromo-2-methylpropene

6

7

7-Chloro-4-phenylhept-2-ene

4-Bromo-3-methylpent-2-ene

1-Chloro-4-(2-methylpropyl)benzene

1

2

3

4

5

6

1

2

3

1

2

3

4

5

12C10.1

​

PSV 2

Q.

(i) 2-Chloro-3-methylpentane

(ii) 1,4-Dibromobut-2-ene

(iii) 1-Bromo-4-sec. butyl-2-methylbenzene

Write structures of the following compounds :

(i) 2-Chloro-3-methylpentane

Sol. 

3

2

1

4

5

(i) 2-Chloro-3-methylpentane

Sol. 

3

2

1

4

5

(i) 2-Chloro-3-methylpentane

Sol. 

(ii) 1,4-Dibromobut-2-ene

3

2

1

4

Sol. 

(iii) 1-Bromo-4-sec. butyl-2-methylbenzene

3

2

1

4

5

6

Sol. 

(iii) 1-Bromo-4-sec. butyl-2-methylbenzene

3

2

1

4

5

6

Sol. 

(iii) 1-Bromo-4-sec. butyl-2-methylbenzene

3

2

1

4

5

6

Sol. 

(iii) 1-Bromo-4-sec. butyl-2-methylbenzene

3

2

1

4

5

6

12C10.1

​

CV 3

​

Nature of C-X bond in Halogen containing Compounds

Nature of C-X bond

>

>

Polar

Nature of C-X bond

<

<

<

Order of size of Halogen Atoms :

Bond

Length

<

<

<

Bond

Strength

<

<

<

Summary

Monohalogen

Compound

Dihalogen

Compound

Polyhalogen

Compound

Alkyl Halides

(Haloalkanes)

Allylic Halides

Benzylic Halides

Vinylic Halides

Aryl Halides

Classification of Halogen containing compounds

12C10.1 Classification, Nomenclature & Nature of C-X Bond

Reference Questions

​

NCERT In-Text Questions: 10.1

​

NCERT Exercise Questions: 10.1, 10.2, 10.3, 10.4

​

Workbook Questions: 1,3

12C10.2

​

Preparation of Haloalkanes

& Haloarenes

12C12.2 Preparation of Haloalkanes and Haloarenes

Learning Objectives

​

Preparation of Haloalkanes from Alcohols (R-OH)

​

Preparation of Haloalkanes from Alkanes

​

Preparation of Haloalkanes from Alkenes

​

Preparation of Haloarenes

12C10.2

​

CV 1

​

Preparation of Haloalkanes from Alcohols(R-OH)

From Alcohols(R-OH)

1. From Lucas Reagent :

Alcohol

Haloalkane

• Carbocation Intermediate

From Alcohols(R-OH)

1. From Lucas Reagent :

Mechanism :

Alcohol

Haloalkane

Carbocation

From Alcohols(R-OH)

1. From Lucas Reagent :

Highlights

• Carbocation Intermediate is formed

• Rearrangement is possible

From Alcohols(R-OH)

Alcohol

Haloalkane

Examples :

Ethanol

Bromoethane

Methanol

Bromomethane

From Alcohols(R-OH)

Alcohol

Haloalkane

Mechanism :

Alcohol

Haloalkane

Repeating

Steps

From Alcohols(R-OH)

Examples :

Ethanol

Chloroethane

Methanol

Bromomethane

From Alcohols(R-OH)

Alcohol

Chloroalkane

Examples :

Ethanol

Chloroethane

Propan-2-ol

2-Chloropropane

Phosphoryl

chloride

From Alcohols(R-OH)

Alcohol

Haloalkane

Ethanol

Chloroethane

Examples :

From Alcohols(R-OH)

Alcohol

Chloroalkane

Mechanism :

Alcohol

Chloroalkane

>

Best method to form Alkylhalides

12C10.2

​

CV 2

​

Preparation of Haloalkanes from Alkanes

From Alkanes by free radical Halogenation

• Proceed via free radical chain mechanism

Step 1. Initiation

Step 2. Propagation

Step 3. Termination

It proceed through following steps :

Mechanism of Halogenation

Initiation Step (Generation of Electrophile)

Mechanism of Halogenation

Initiation Step(Generation of Electrophile)

Mechanism of Halogenation

Initiation Step

Chlorine Free Radical

Mechanism of Halogenation

Propagation Step

Mechanism of Halogenation

Propagation Step

Methyl Free Radical

Mechanism of Halogenation

Propagation Step

Mechanism of Halogenation

Repeats

Propagation Step

Chloromethane

Mechanism of Halogenation

Termination Step

• Reactivity of Halogens towards alkane :

• Rate of replacement of hydrogens of alkanes :

• Fluorination is too violent to be controlled.

Halogenation

Radicals formed is more stable

• Iodination is very slow and a reversible reaction

Gets Consumed

Halogenation

12C10.2

​

PSV 1

Q.

Write the major mono-chlorination product of the following reactions:

a.

b.

Sol.

Relative reactivity of alkanes towards chlorination :

1

3.8

4.5

Alkane :

Ratio of reactivity :

a.

(major product)

Sol.

b.

(major product)

12C10.2

​

CV 3

​

Preparation of Haloalkanes from Alkenes

Addition of Hydrogen Halides

Alkene

Alkyl Halide

Mechanism

Carbocation

• Carbocation is form hence rearrangement can occur if possible.
• In case of Chiral carbon : Racemic Mixture will form

Hydrogen Halide

Addition of Hydrogen Halides

Examples :

Symmetrical Alkenes

Ethene

Bromoethane

But-2-ene

2-Bromobutane

Addition of Hydrogen Halides

(More Stable)

(Less Stable)

Propene

Unsymmetrical Alkenes

Examples :

(Major Product)

(Minor Product)

Markovnikov rule

H or electrophilic part of the attacking molecule gets attached to that C-atom which have more number of H atoms

Example :

1 H

2 H

2-Bromopropane

Major Product

Example :

1-Bromobutane

Anti Markovnikov addition

Peroxide effect or Kharash effect

Mechanism

Anti Markovnikov addition

Genertion of Phenyl free Radical :

Genertion of Bromine free Radical :

Benzoyl peroxide

Phenyl fee radical

Bromine fee radical

Phenyl fee radical

(more stable)

(less stable)

(Major Product)

(Minor Product)

Anti Markovnikov addition

1-Bromoalkane

2-Bromoalkane

Case : 1

Case : 2

12C10.2

​

PSV 2

Q.

Pause the video

Time duration : 3 minutes

Sol.

Rearrangement

2-Bromo-2-methylbutane

3-Methylbut-1-ene

Without Peroxide

Q.

Sol.

With Peroxide

3-Methylbut-1-ene

• No Rearrangement and Anti Markovnikov Addition

1-Bromo-3-methylbutane

Q.

Addition of Halogens

Alkene

Vicinal Dihalide

Mechanism

Non-Classical cation

Highlights of addition of Halogens

Halogen Exchange

1. Finkelstein Reaction :

Haloalkane

Iodoalkane

Dry Acetone

Example :

Dry Acetone

Bromomethane

Iodomethane

Halogen Exchange

2. Swarts Reaction :

Bromomethane

Fluoromethane

12C10.2

​

CV 4

​

Preparation of Haloarenes

From Hydrocarbons by Electrophilic Substitution

Toulene

o-Halotoulene

p-Halotoulene

Mechanism

Generation of Electrophile :

Electrophile

C

C

C

C

C

H

H

H

H

H

C

Mechanism

C

C

C

C

C

H

H

H

H

H

C

Mechanism

C

C

C

C

C

H

H

H

H

H

C

Mechanism

C

C

C

C

C

H

H

H

H

H

C

Mechanism

C

C

C

C

C

H

H

H

H

H

X

C

Mechanism

C

C

C

C

C

H

H

H

H

H

X

C

Mechanism

C

C

C

C

C

H

H

H

H

H

C

Mechanism

X

C

C

C

C

C

H

H

H

H

H

C

Mechanism

X

C

C

C

C

H

H

H

H

H

C

C

Mechanism

X

C

C

C

C

H

H

H

H

H

C

C

Mechanism

X

C

C

C

C

H

H

H

H

C

C

Mechanism

X

C

C

C

C

H

H

H

H

C

C

Mechanism

X

C

C

C

C

H

H

H

H

X

C

C

Mechanism

o-Halotoulene

C

C

C

C

H

H

H

H

X

C

C

Mechanism

p-Halotoulene

From Amines by Sandmeyer’s reaction

Aniline

Benzene diazonium

Halide

Halobenzene

Mechanism

Electrophile

Formation of electrophile

Mechanism

Formation of Benzene diazonium salt

Aniline

Mechanism

Formation of Benzene diazonium salt

or

or

Mechanism

Haloarene from Benzene diazonium salt

Benzene diazonium

salt

Chlorobenzene

Benzene diazonium

salt

Iodobenzene

Iodobenzene

ConcepTest

​

Ready for Challenge

Q.

Write the product of the following Reaction :

Pause the video

Time duration : 2 minutes

Sol.

Hydride Shift

2-Chloro-2,3-dimethyl butane

Summary

Preparation of Haloalkanes :

• From Alkanes :

• From Alcohols :

Summary

Preparation of Haloalkanes :

• From Alkenes :

• Halogen Exchange :

Dry Acetone

Summary

Preparation of Haloarenes :

• From Aromatic hydrocarbons :

12C10.2 Preparation of HaloAlkanes & Haloarenes

Reference Questions

​

NCERT In-Text Questions: 10.4, 10.5

​

NCERT Exercise Questions: 10.7, 10.14 ( i, vi, vii, viii), 10.19( i, viii, x, xii)

​

Workbook Questions: 7, 10, 11, 18(i), 19( i, iii)

12C10.3

​

Properties of Haloalkanes

& Haloarenes-1

12C10.3 Properties of Haloalkanes & Haloarenes-1

12C10.3

​

CV 1

​

Physical Properties of Haloalkanes & Haloarenes

Physical Properties

• Pure Alkyl halides are colourless

Bromides and Iodides develop colour when exposed to light

Colour & Physical state :

Ethyl Iodide

Colourless

Physical Properties

• Pure Alkyl halides are colourless

Bromides and Iodides develop colour when exposed to light

Colour & Physical state :

Ethyl Iodide

Yellow

Initial Chlorides, Bromides & Chlorofluoromethanes are gas, whereas higher members are liquids & solids

Physical Properties

• For isomeric Haloalkanes :

6-C

6-C

Low Van der Waals forces

Low boiling point

• Boiling points of Chlorides, Bromides and Iodides are considerably higher than those of the hydrocarbons of comparable molecular mass.

Boiling Point :

Physical Properties

• Order of Boiling point for compounds having same alkyl group :

• Boiling point for isomeric dihalobenzenes are very nearly the same

B.P

453 K

446 K

448 K

Boiling Point :

Physical Properties

• Melting point for isomeric dihalobenzenes :

M.P

256 K

249 K

323 K

Symmetrical

High Melting point

• The density of Halogen containing Compounds increases with increase in number of C-atoms, X-atoms and atomic mass of the X-atoms

Melting Point :

Density :

Physical Properties

• Very less soluble in water

Alkyl halide

Less Polar

Solubility :

Hydrogen

Bonding

ConcepTest

​

Ready for Challenge

Q. Arrange the following compounds in order of their increasing b.p.

1-Chloropropane, 1-Chlorobutane, 2-Chloro-2-methylpropane,

1-Chloropentane

Pause the video

Time duration: 1 minute

Decreases with increase of branching in carbon chain.

Sol.

Increases with increase in the no. of C-atoms.

Boiling points of Haloalkanes -

<

<

<

1-Chloropropane

2-Chloro-2-methyl

propane

1-Chlorobutane

1-Chloropentane

Chemical Properties of Haloalkanes

The reactions of Haloalkanes can be divided into the following categories

Nucleophilic substitution

Elimination reactions

Reaction with metals

Chemical Properties of Haloalkanes

The reactions of Haloalkanes can be divided into the following categories

Nucleophilic substitution

Elimination reactions

Reaction with metals

Nucleophilic Substitution Reactions

What is Nucleophile ?

The reaction in which a nucleophile replaces already existing nucleophile in a molecule is called nucleophilic substitution reaction.

• Nucleus loving

• Electron rich

Nucleophiles

Negatively Charged

Lone Pairs

Nucleophilic Substitution Reactions

General Nucleophilic Substitution Reaction for Haloalkanes :

Nucleophilicity :

Nucleophilic Substitution Reactions

General Nucleophilic Substitution Reaction for Haloalkanes :

Nucleophilicity :

Nucleophilic Substitution Reactions

General Nucleophilic Substitution Reaction for Haloalkanes :

Nucleophilicity :

Nucleophilic Substitution Reactions

Nucleophilic Substitution Reactions

• Rate of reaction depends upon substrate as well as Attacking Nucleophile

C

H

H

H

Cl

C

H

H

H

Cl

C

H

H

H

Cl

C

H

H

H

Cl

Pentavalent Transition state

Leaving Group

C

H

H

H

Inversion of Configuration

Single step reaction

Formation of Pentavalent Transition State

Inversion of Configuration

12C10.3

​

PSV 1

Sol.

Alkyl halide

Ambident Nucleophile

Alkyl cynide

Alkyl halide

Alkyl isocynide

More Stable

(Major product)

Sol.

Free lone pair

Alkyl halide

Alkyl isocynide

Optical Activity

Ordinary

Light

Nicol

Prism

Plane

Polarised

Light

or

Optically Inactive Compound

Or

Racemic mixture

Dextrorotatory

(d) Or (+)

Laevo-rotatory

(l) Or (-)

Optical Isomers

Optically Active

Asymmetry & Chirality

Object

Mirror Image

Non-Superimposable

Superimposable

Asymmetric

Symmetric

Mirror

Asymmetry & Chirality

Chiral Carbon

Non-Superimposable

Optically Active

Asymmetry & Chirality

*

*

*

Lactic acid

Tartaric acid

Examples of Opticaly Active compounds :

* Chiral carbon

Retention, Inversion & Racemisation

Optically Active

Retention, Inversion & Racemisation

B

A

A + B in equal amount

Same Spatial Arrangement

Of Bonds

Different Spatial Arrangement

Of Bonds

Retention Product

Inversion Product

Racemisation

Optically Inactive

Enantiomers & Diastereomers

Enantiomers :

Stereoisomers that are not mirror images of one another and are non-superimposable on one another.

Stereoisomers that are non-superimposable mirror images of one another.

Diastereomers :

d-lactic acid

l-lactic acid

3-Bromo butan-2-ol

3-Chlorobutan-2-ol

(i)

(ii)

(iii)

(iv)

Non Superimposable mirror image

Non Superimposable mirror image

Enantiomers

Enantiomers

Enantiomers & Diastereomers

3-Chlorobutan-2-ol

(i)

(ii)

(iii)

(iv)

Neither Superimposable nor mirror image

Diastereomers

Enantiomers & Diastereomers

Example : 2-Bromobutane :

Inversion of configuration

ConcepTest

​

Ready for Challenge

Q.

How many chiral carbon are present in the following compound.

​

Pause the video

Time duration: 1 minute

Q.

How many chiral carbon are present in the following compound.

​

Sol.

*

*

*

*

* Chiral carbon

* Chiral carbon