28 June 2020
NVS HYD RO
1
OBJECTIVES
After studying this unit, STUDENTS will be able to
• Name haloalkanes and haloarenes according to the IUPAC
system of nomenclature from their given structures;
• Describe the reactions involved in the preparation of
haloalkanes and haloarenes and understand various
reactions that they undergo;
• Correlate the structures of haloalkanes and haloarenes with
various types of reactions;
• Use stereochemistry as a tool for understanding the reaction
mechanism;
• Appreciate the applications of organo-metallic compound;
• Highlight the environmental effects of polyhalogen
compounds.
28 June 2020
NVS HYD RO
2
OUTLINE
1. INTRODUCTION,CLASSIFICATION,
NOMENCLATURE
2. PHYSICAL PROPERTIES OF HALO
ALKANES & HALO ARENES
3. METHODS OF PREPARATION
4. CHEMICAL PROPERTIES
5. OPTICAL ISOMERISM
6. SN1 & SN2 REACTIONS
7. POLY HALOGEN COMPOUNDS
28 June 2020
NVS HYD RO
3
What is meaning of haloalkane?
Organic compounds formed by replacement of one or
more hydrogen atom/s by halogen atom/s. from
Hydrocarbon
Ex: chloromethane, Dichloromethane etc.
28 June 2020
NVS HYD RO
4
Examples for haloalkanes
28 June 2020
NVS HYD RO
5
What is meaning of haloarene?
If one or more hydrogen is displaced by
halogen atom/s in aromatic ring ,
product is called as Haloarenes
28 June 2020
NVS HYD RO
6
Importance of Halogen
derivative.
Haloderivative
Organic
compounds
many importance for Mankind:
1.As solvents for non-polar compounds.
28 June 2020
NVS HYD RO
have
2.Chloramphenicol
(medicine) to treat typhoid
fever.
28 June 2020
NVS HYD RO
8
3.Chloroquine
(medicine) used
to treat malaria.
4. Some fluorinated
compounds are being
developed as blood substitute
in surgery.
28 June 2020
NVS HYD RO
9
5.Halothane is used as anaesthatic during
surgery.
28 June 2020
NVS HYD RO
10
6.THYROXINE is used in the treatment of
Goitre disease
28 June 2020
NVS HYD RO
11
7. As starting materials for synthesis of
many compounds.
28 June 2020
NVS HYD RO
12
28 June 2020
NVS HYD RO
13
Classification of Haloderivatives
Based on
Number of
Halogen atoms
Monohalogen
Based on the hybridisation of C−atom
of C−X bond of monohalocompounds
Compounds
containing sp3 C−X
bond (X = F, Cl, Br, I).
Dihalogen
Compounds containing
sp2 C−X bond
Polyhalogen
28 June 2020
NVS HYD RO
Monohalo derivatives
28 June 2020
NVS HYD RO
15
Dihalo derivatives
28 June 2020
NVS HYD RO
16
Dihalo derivatives
28 June 2020
NVS HYD RO
17
Trihalo derivatives
28 June 2020
NVS HYD RO
18
Compounds containing sp3 C−X
bond (X = F, Cl, Br, I).
28 June 2020
NVS HYD RO
19
28 June 2020
NVS HYD RO
20
28 June 2020
NVS HYD RO
21
28 June 2020
NVS HYD RO
22
Allylic halides
28 June 2020
NVS HYD RO
23
Benzylic halides
28 June 2020
NVS HYD RO
24
2
sp
Compounds containing
C−X bond (X = F, Cl, Br, I).
28 June 2020
NVS HYD RO
25
Vinylic halides
halogen atom is bonded to a sp2 hybridised carbon
atom of a carbon-carbon double bond (C = C).
28 June 2020
NVS HYD RO
2626
Aryl halides
halogen atom is directly bonded to the sp2
hybridised carbon atom of an aromatic ring.
28 June 2020
NVS HYD RO
2727
28 June 2020
NVS HYD RO
2828
ORDER OF NAMING Halogen compounds
PREFIXES
•
•
•
•
F
Cl
Br
I
Floro
Chloro
Bromo
Iodo
28 June 2020
WORD
ROOT
• 1C meth
• 2C eth
• 3C Prop
NVS HYD RO
PRIMARY
SUFIXES
• ane
• ene
• yne
2929
3
1-Bromo +
2
1
prop
+ane
1-Bromopropane
28 June 2020
NVS HYD RO
3030
Example-2
28 June 2020
NVS HYD RO
31
Example-3
Name the following:
Br
Cl
28 June 2020
Cl
NVS HYD RO
32
Solution
Name the following:
Br
bromocyclopentane
Cl
1,3-dichlorocyclohexane
Cl
28 June 2020
NVS HYD RO
33
Q-1
28 June 2020
NVS HYD RO
34
Q-2
28 June 2020
NVS HYD RO
35
Q3
28 June 2020
NVS HYD RO
36
Q-4
28 June 2020
NVS HYD RO
37
Q-5
28 June 2020
NVS HYD RO
38
Q-6
28 June 2020
NVS HYD RO
39
Nature of C-X bond
Now THINK why of the following:
1. The C-X bond in haloalkanes is polar in nature.
2. C-X bond length increases as C-F< C-Cl < C-Br <C-I.
3. C-F bond is less reactive as compared to C-I bond.
4. Order of Dipole moment is CH3-Cl > CH3-F> CH3Br >CH3I
5. The dipole moment of chlorobenzene is lower than that of
cyclohexylchloride.
28 June 2020
NVS HYD RO
40
28 June 2020
NVS HYD RO
41
PHYSICAL STATE
28 June 2020
NVS HYD RO
42
28 June 2020
NVS HYD RO
43
28 June 2020
NVS HYD RO
44
BOILING POINT
28 June 2020
NVS HYD RO
45
BOILING POINT
28 June 2020
NVS HYD RO
46
BOILING POINT
28 June 2020
NVS HYD RO
47
DENSITY
28 June 2020
NVS HYD RO
48
DENSITY
28 June 2020
NVS HYD RO
49
METHODS OF PREPARATION OF
ALKYL HALIDES
1.
2.
3.
4.
FROM ALKANE
FROM ALKENE
FROM ALCOHOL
BY HALOGEN EXCHANGE
METHOD
28 June 2020
NVS HYD RO
50
1.FROM ALKANE
28 June 2020
NVS HYD RO
51
2.FROM ALKENE
28 June 2020
NVS HYD RO
52
28 June 2020
NVS HYD RO
53
28 June 2020
NVS HYD RO
54
28 June 2020
NVS HYD RO
55
FROM ALCOHOL
28 June 2020
NVS HYD RO
56
3. FROM ALCOHOL
28 June 2020
NVS HYD RO
57
28 June 2020
NVS HYD RO
58
28 June 2020
NVS HYD RO
59
28 June 2020
NVS HYD RO
60
FROM ALCOHOL
28 June 2020
NVS HYD RO
61
28 June 2020
NVS HYD RO
62
4. BY HALIDE EXCHANGE
28 June 2020
NVS HYD RO
63
28 June 2020
NVS HYD RO
64
28 June 2020
NVS HYD RO
65
CHEMICAL PROPERTIES
28 June 2020
NVS HYD RO
66
1.Nucleophilic substitution reactions
28 June 2020
NVS HYD RO
67
Order of reactivity
28 June 2020
NVS HYD RO
68
28 June 2020
NVS HYD RO
69
28 June 2020
NVS HYD RO
70
Williamsons synthesis
28 June 2020
NVS HYD RO
71
28 June 2020
NVS HYD RO
72
28 June 2020
NVS HYD RO
73
28 June 2020
NVS HYD RO
74
28 June 2020
NVS HYD RO
75
Elimination Reactions
28 June 2020
NVS HYD RO
76
28 June 2020
NVS HYD RO
77
28 June 2020
NVS HYD RO
78
Reaction with Mg metal
28 June 2020
NVS HYD RO
79
WURTZ REACTION
28 June 2020
NVS HYD RO
80
Stereochemistry-II
Optical Isomerism
28 June 2020
NVS HYD RO
81
Isomers
Same molecular formula
Constitutional
Differ in bond connectivity
28 June 2020
Stereoisomers
Differ in three dimensional
arrangement
NVS HYD RO
82
Stereoisomers
Differ in three dimentsional arrangement
Configurational
Differ in groups or atoms
28 June 2020
NVS HYD RO
Conformational
Due to free rotation
83
Configurational
Differ in groups or atoms
Geometrical
Due to restricted rotation
Optical
Due to Chirality
Carbon- carbon double bond
Carbon- nitrogen double bond
Nitrogen-nitrogen double bond
Ring Compounds
28 June 2020
NVS HYD RO
84
Optical Isomerism
Existence of two or more isomers of a
substance that differ in their optical activity
Optical activity : the property of a molecule
to rotate the plane of plane-polarized light.
28 June 2020
NVS HYD RO
85
28 June 2020
NVS HYD RO
86
28 June 2020
NVS HYD RO
87
28 June 2020
NVS HYD RO
88
What is plane-polarized light ?
Ordinary light consists of oscillating
electrical and magnetic fields or waves
vibrating in all directions perpendicular to
the direction the light beam
28 June 2020
NVS HYD RO
89
On passing the ordinary light through a
device called Polarizer, its oscillations in all
but one direction are blocked and the light
emerging from the polarizer oscillates in
only one plane
P
o
l
a
r
i
z
e
r
This is called plane polarized light
28 June 2020
NVS HYD RO
90
Plane-polarized light
Magnetic field
Electrical field
Plane polarized light
Oscillating
electrical field
The plane polarized light has mutually
perpendicular electric and magnetic fields.
However, it is the electrical component
that is more
significant
28 June 2020
NVS HYD RO
91
28 June 2020
NVS HYD RO
92
An optically active substance interacts
with the plane polarized light in such a way
that the plane of light rotates.
P
o
l
a
r
i
z
e
r
28 June 2020
a
Solution of
optically
active
substance
NVS HYD RO
93
The substance that rotates the plane of
polarized light to the right is called
dextrorotatory and the one that rotates
it to the left is called laevorotatory
Dextrorotatory : rotation to right
(The angle of rotation, a, is considered to be positive (+).)
Laevorotatory : rotation to left
(The angle of rotation, a, is considered to be negative (-).)
28 June 2020
NVS HYD RO
94
28 June 2020
NVS HYD RO
95
LEAVO ROTATORY COMPOUND
28 June 2020
NVS HYD RO
96
ENANTIOMERS
28 June 2020
NVS HYD RO
97
Cause of Optical Activity
Optical isomerism is due to chirality
in a molecule
Greek cheir : hand
Chiral objects have a "handedness"
The chirality of an object is related to
its symmetry rather lack of it
28 June 2020
NVS HYD RO
98
The objects with ‘HANDEDNESS’ cannot
be superimposed on their mirror images.
e.g., hands or gloves
M
I
R
R
O
R
28 June 2020
NVS HYD RO
99
A right hand cannot be
superimposed on a Left hand
28 June 2020
NVS HYD RO
100
Is a scissor chiral ?
28 June 2020
NVS HYD RO
101
The objects that do not have a handedness can
be superimposed on their mirror image.
e.g., a butterfly
M
I
R
R
O
R
The objects that are superimposable on their
mirror images are said to be achiral.
28 June 2020
NVS HYD RO
102
A butterfly is symmetric- one half of its
body exactly overlaps its other half
28 June 2020
NVS HYD RO
103
Some other examples are:
28 June 2020
NVS HYD RO
104
CHIRAL [ ASYMMETRIC]
28 June 2020
ACHIRAL [SYMMETRIC]
NVS HYD RO
105
CHIRAL [ ASYMMETRIC MOLECULES]
28 June 2020
NVS HYD RO
106
Bromochlorofluoromethane
M
I
R
R
O
R
28 June 2020
NVS HYD RO
107
Non-superimposable hence chiral
28 June 2020
NVS HYD RO
108
 Compounds that are not superimposable
on their mirror images will show optical
isomerism
 These isomers are called enantiomers
 One of the isomer is dextrorotatory
and the other is laevorotatory
28 June 2020
NVS HYD RO
109
In a pair of optically active enantiomers,each
enantiomer rotates the plane of polarized
light in equal and opposite directions.
P
o
l
a
r
i
z
e
r
Solution
of
Enantiomer
1
Solution
of
Enantiomer
2
However, a mixture of two in equal proportions
will be optically inactive and is called a racemic
mixture
28 June 2020
NVS HYD RO
110
28 June 2020
NVS HYD RO
111
Bromochloromethane
M
I
R
R
O
R
28 June 2020
NVS HYD RO
112
The mirror image is superimposable hence
the molecule is achiral and does not show
optical isomerism
28 June 2020
NVS HYD RO
113
Bromomethane
M
I
R
R
O
R
28 June 2020
NVS HYD RO
114
The mirror image is superimposable hence
the molecule is achiral and does not show
optical isomerism
28 June 2020
NVS HYD RO
115
Chirality (non-superimposibility of
mirror image) is a necessary and
sufficient condition for a molecule
to show optical activity
28 June 2020
NVS HYD RO
116
Recall the molecule of bromochlorofluoromethane
The carbon atom is attached to
four different groups.
Such a carbon atom is known as
asymmetric carbon atom.
A molecule possessing asymmetric
carbon atom shows enantiomerism.
Two optically active isomers (one dextroand other laevorotatory) exist
28 June 2020
NVS HYD RO
117
FISCHER PROJECTION
A two dimensional representation of a three
dimensional molecule
CH3
CH3
CH(CH3)2
H
H
CH2OH
28 June 2020
CH(CH3)2
CH2OH
NVS HYD RO
118
28 June 2020
NVS HYD RO
119
Nucleophilic Substitution
 A substitution reaction where the reagent
is a nucleophile

A typical reaction of alkyl halides
R
X
+
R
Nu
Nu
+
X
 May follow SN2, SN1 and SNi mechanisms
 Depends on
 Nature of substrate
 Reagent
 Reaction conditions
28 June 2020
NVS HYD RO
120
SN1 Mechanism
SN1 : Substitution Nucleophilic
Unimolecular
Favoured
With neutral or weak Nucleophiles
(water, alcohols,amines)
(R)3CX
28 June 2020
+
(R)3COH
H2O
NVS HYD RO
+
HX
121
SN1 Mechanism
Unimolecular
Rate depends on conc. of ONE species
Rate  k[RX ]
;
Ist Order
Depends on alkyl halide and NOT nucleophile
Two steps
The first step is slow or Rate-determining
The second step is the fast step
28 June 2020
NVS HYD RO
122
The SN1 Mechanism
Step 1
Cleavage of C-X bond (Formation of carbocation)
R3C
X
-X
R3C
+
( slow)
Step 2
Attack of nucleophile (Formation of product)
+
R3C + Nu
28 June 2020
R3C
NVS HYD RO
Nu (fast)
123
The SN1 Mechanism
Example
(CH3)3CBr
+
(CH3)3COH
H2O
+
HBr
Experimental facts
Doubling substrate conc. : Rate doubled
Doubling nucleophile conc. : Rate unchanged
Thus
Rate a [(CH3)3CBr]
Rate = k [(CH3)3CBr]
28 June 2020
NVS HYD RO
124
CH3
H3C
C
CH3
CH3
+
Br
C
H3C
+
Br
CH3
CH3
H2O
H3C
C
CH3
+
OH2
+ H2O
H O+
H3C
C
OH
3
CH3
28 June 2020
NVS HYD RO
CH3
125
Carbocations
 Reactive intermediates

Positively charged carbon
 Planar (sp2 hybridised)
H
H
C
H
H
C
H
H
H
H
C
>
C+
H
H
C
H
H
>
C+
H
C
H
H
H
H
C
H
C+
H
>
H
H
C+
H
H
H
Hyperconjugation stabilises the positive charge
28 June 2020
NVS HYD RO
126
Carbocations are planar
Nucleophile can attack
from both sides
Product is a racemic
mixture
Rate depends on stability of carbocation
Decrease in the order 3o > 2o > 1o
Resonance stabilised carbocations favoured
(allylic, benzylic)
28 June 2020
NVS HYD RO
127
Order of Reactivity in SN1
Directly related to the stability of
intermediate i.e. the Carbonium ion or the
Carbocation
The order of reactivity is
R
R
R
C+
R
>
H
C+
R
>
H
R
C+
>
H
C+
H
Tertiary > Secondary > Primary >
28 June 2020
H
NVS HYD RO
H
Methyl
128
SN2 Mechanism
SN2 : Substitution Nucleophilic Bimolecular
Favoured with strong nucleophiles
R
R
R
C
X
+
HO
HO
R
28 June 2020
R
C
+
Br
R
NVS HYD RO
129
SN2 Mechanism
Bimolecular
Rate depends on the conc. of TWO species
nucleophile and substrate
R
HO
R
C
R
28 June 2020
X

HO
R
R
R
C

X
R
NVS HYD RO
HO
R
C
+
X
R
130
H
H
H
C
X
+
HO
HO
H
H
C
+
Br
H
Experimental facts
Doubling nucleophile conc. : Rate doubles
Doubling substrate conc.
Thus
28 June 2020
: Rate doubles

Rate  k[CH 3 Br ][OH ]
NVS HYD RO
131
SN2 Mechanism
One-step mechanism (Concerted )
Attack of nucleophile and removal of
leaving group is simultaneous
Leaving group leaves OPPOSITE of the attacking
nucleophile
28 June 2020
NVS HYD RO
132
H
HO
H
C
H
Br

HO
H
H
H
C

Br
H
HO
H
C
+
Br
H
There is only one transition state
28 June 2020
NVS HYD RO
133
Stereochemistry of SN2 Reaction
Attack from side opposite to the leaving group
Inversion of Configuration (Walden
inversion)
28 June 2020
NVS HYD RO
134
Stereochemistry of SN2 Reaction
Attack from side opposite to the leaving group
Inversion of Configuration (Walden
inversion)
28 June 2020
NVS HYD RO
135
Steric Effect in SN2 Reactions
Reactivity
150
28 June 2020
1
0.01
NVS HYD RO
0.0001
136
Reaction with KCN and AgCN
CH3CH2
Br
+
KCN
CH3CH2
C
+
KBr
C
+
N
Propanenitrile
CH3CH2
Br
+
CH3CH2
AgCN
N
KBr
Propaneisonitrile
28 June 2020
NVS HYD RO
137
SN1 Vs SN2
Mechanism
Unimolecular (two steps)
Bimolecular (one step)
Rate of Reaction
Depends only on the
substrate
Depends on nucleophile
and substrate
Nucleophiles
Favoured by neutral
Nucleophiles
28 June 2020
Favoured by strong
Nucleophiles
NVS HYD RO
138
SN1 Vs SN2
Solvents
Favoured by polar
protic solvents
Favoured by polar aprotic
solvents
Alkyl group
Favoured by Bulky
alkyl groups
Favoured by less
substituted alkyl groups
Stereochemistry
Racemic mixture
28 June 2020
Inversion of configuration
NVS HYD RO
139
Some Problems
1.Which one of the following will be faster
and why?
i) CH3Br + HOH
CH3OH + HBr
CH3OCOCH3
ii) CH3Br + CH3COO-
28 June 2020
NVS HYD RO
140
2. Arrange the following in increasing order of
reactivity towards SN1 reactions:
i) CH3CH2CH2Br, CH3CH2CH(Br)CH3, (CH3)3CBr
ii)
28 June 2020
(CH3)2CHBr , (CH3)2CHCl , (CH3)2CHI
NVS HYD RO
141
3. Arrange the following in increasing
order of reactivity towards SN2 reactions:
i) (CH3)2CHBr , (CH3)3CBr , CH3CH2Br
ii) CH3CH2Br , CH3CH2Cl , CH3CH2I
28 June 2020
NVS HYD RO
142
28 June 2020
NVS HYD RO
143
28 June 2020
NVS HYD RO
144
28 June 2020
NVS HYD RO
145
28 June 2020
NVS HYD RO
146
28 June 2020
NVS HYD RO
147
28 June 2020
NVS HYD RO
148
28 June 2020
NVS HYD RO
149
28 June 2020
NVS HYD RO
150
CHEMICAL PROPERTIES OF HALO
ARENES
28 June 2020
NVS HYD RO
151
Reasons for the less rectivity of
chlorobenzene
28 June 2020
NVS HYD RO
152
Reasons for the less rectivity
of chlorobenzene
28 June 2020
NVS HYD RO
153
Reasons for the less rectivity
of chlorobenzene
28 June 2020
NVS HYD RO
154
Reasons for the less rectivity
of chlorobenzene
28 June 2020
NVS HYD RO
155
O- & p- directing
28 June 2020
NVS HYD RO
156
NUCLOPHILIC SUBSTITUTION
REACTION
28 June 2020
NVS HYD RO
157
NUCLOPHILIC
SUBSTITUTION REACTION
28 June 2020
NVS HYD RO
158
NUCLOPHILIC
SUBSTITUTION REACTION
28 June 2020
NVS HYD RO
159
1.HALOGENATION
28 June 2020
NVS HYD RO
160
2. NITRATION
28 June 2020
NVS HYD RO
161
3.SULPHONATION
28 June 2020
NVS HYD RO
162
4. FRIEDEL-CRAFTS
ALKYLATION
28 June 2020
NVS HYD RO
163
REACTION WITH METALS
28 June 2020
NVS HYD RO
164
4. FRIEDEL-CRAFTS
ALKYLATION
28 June 2020
NVS HYD RO
165
REACTION WITH METALS
28 June 2020
NVS HYD RO
166
POLY HALOGEN
COMPOUNDS
28 June 2020
NVS HYD RO
167
Dichloromethane
28 June 2020
NVS HYD RO
168
Tetrachloromethane
28 June 2020
NVS HYD RO
169
Triiodomethane
28 June 2020
NVS HYD RO
170
Freons
28 June 2020
NVS HYD RO
171
DDT
28 June 2020
NVS HYD RO
172
SUMMARY
1. INTRODUCTION,CLASSIFICATION,
NOMENCLATURE
2. PHYSICAL PROPERTIES OF HALO
ALKANES & HALO ARENES
3. METHODS OF PREPARATION
4. CHEMICAL PROPERTIES
5. OPTICAL ISOMERISM
6. SN1 & SN2 REACTIONS
7. POLY HALOGEN COMPOUNDS
28 June 2020
NVS HYD RO
173
HOME WORK
1. Why is sulphuric acid is not used during reaction of alcohols with
KI?
2. Arrange each set of compounds in order of increasing boiling
poings. i) Bromo Ethane , Bromoform,
Chloro
methane,
Dibromo methane
(ii) 1-Chloro Propane, Isopropyl chloride, 1-chloro butane
3. Predict the order of reactivity of the following compounds in SN1
& SN2 reactions. (i) The four isomeric bromo butanes
( ii) C6H5CH2Br, C6H5CH2 (C6H5 )Br, C6H5CH2 (CH3)Br,
C6H5CH2 (CH3 )(C6H5 )Br
4. Although Chlorine is an electron with drawing group yet it is orho
para directing in electrophilic aromatic substitution
reactions. Why?
5. Which alkyl halide from the following pairs would you expect to
react more rapidly by SN2 mechanism? Explain your
answer?
(A) CH3-CH2-CH2-CH2-Br & CH3-CH2-CHBr –CH3
28 June 2020
HYD RO
174
(B)CH3-CH2-CHBr –CH3 NVS
& C(CH
3)3Br
HOME WORK
6. alo alkanes react with KCN to form alkyl cyanides as main
product while AgCN forms isocyanides as the chief product.
Explain.
7. COMPLETE THE FOLLOWING
28 June 2020
NVS HYD RO
175
HOME WORK
8. Explain the following named reactions
(a) Williamson’s synthesis
(b) Swarts reaction
©Finkelstein reaction
(d)Sand mayers reaction
(e) Gatterman reaction
(f)Fittig reaction
9.What are ambident nucleophiles? Explain with an example.
10.What happens when
(i)
n-butyl chloride is treated with alcoholic KOH
(ii) Bromobenzene is treated with Mg in the presence of dry ether
(iii) Chlorobenzene is subjected to hydrolsis.
(iv) Ethyl chloride is treated with aqueous KOH
(v)28 June
Methyl
KCN?
2020 chloride is treated with
NVS HYD
RO
176
28 June 2020
NVS HYD RO
177