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B) From Hydrocarbon:-: A) by Free Radical Halogenation Reaction

This document discusses several methods for synthesizing haloalkanes from hydrocarbons and alkenes, including: 1) Free radical halogenation of alkanes using chlorine or bromine in the presence of sunlight yields chloro- or bromoalkanes. Excess halogen leads to polyhaloalkanes. 2) Electrophilic substitution of benzene or its derivatives with chlorine or bromine in the presence of Fe or FeCl3 catalysts yields ortho- and para-substituted products, with para being the major product due to steric hindrance. 3) The Sandmeyer reaction converts aniline to chloro-, bromo-, or iodob

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169 views2 pages

B) From Hydrocarbon:-: A) by Free Radical Halogenation Reaction

This document discusses several methods for synthesizing haloalkanes from hydrocarbons and alkenes, including: 1) Free radical halogenation of alkanes using chlorine or bromine in the presence of sunlight yields chloro- or bromoalkanes. Excess halogen leads to polyhaloalkanes. 2) Electrophilic substitution of benzene or its derivatives with chlorine or bromine in the presence of Fe or FeCl3 catalysts yields ortho- and para-substituted products, with para being the major product due to steric hindrance. 3) The Sandmeyer reaction converts aniline to chloro-, bromo-, or iodob

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Raju kumar
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B] From Hydrocarbon:-

a) By free radical Halogenation reaction :-


When alkane is treated with Chlorine or Bromine in the presence of Sunlight the free
radical halogenation reaction take place and results the formation of Chloro or Bromo alkane. If
halogen is in excess amount then polyhaloalkane is formed.
* Chemical equation from Video
* Related NCERT questions
Example – 10.5, Intext – 10.3, 10.4

b) By electrophilic substitution reaction:-


When benzene or derivative of benzene is treated with chlorine or bromine in the presence
of Lewis acid catalyst like Fe or FeCl3, electrophilic substitution reaction take place and results
the formation of ortho and para derivative.
Due to stearic hindrance ortho derivative is unstable and therefore para derivative is
formed as a major product.

Note:- The reaction of halogen in the presence of sunlight give free radical halogenation reaction
in which halogen is attached with sp3 hybridised carbon atom while in dark and in the presence of
iron, electrophilic substitution reaction take place in which halogen is attached with sp2
hybridised carbon atom.
* Chemical equation from Video
* Related NCERT questions
Exercise – 10.5
c) Sandmeyer’s reaction:-
When aniline is treated with nitrous acid benzene diazonium halide is formed which on
treatment with cuprous halide give chloro or bromo benzene and on treatment with potassium
iodide results the formation of Iodobenzene.
* Chemical equation from Video
C] By Halogen exchange Method:-
When chloro or bromoalkane is treated with Sodium Iodide in the presence of dry acetone
then corresponding Iodoalkane is formed. This reaction is known as Finkelstein reaction.
When chloro or bromoalkane is treated with metal fluoride like AgF, Hg2F2, CoF2 or SbF3
then corresponding Fluoroalkane is formed. The reaction is called Swarts reaction.
* Chemical equation from Video
D] From Alkene:-
a) By addition of Halogen:-
When alkene is treated with Chlorine or Bromine the addition reaction take place and
results the formation of Vicinal dihalide.

Note:- When alkene is treated with Bromine the addition reaction take place and results the
formation of Vicinal dibromoalkane. The reaction is used to test the unsaturation of hydrocarbon
because only unsaturated hydrocarbon can show the addition reaction and decolourise the
bromine solution.
* Chemical equation from Video
b) By addition of Hydrogen halide:-
When alkene is treated with Hydrogen halide the addition reaction take place and results
the formation Haloalkane.
CH2 = CH2 + HCl  CH3-CH2Cl
In the case of unsymmetrical alkene the addition reaction obey Markownikov’s rule. It
states that “ The negative part of attacking reagent attach with that carbon atom which has
comparatively less number of Hydrogen atom.”

Note:- If the reaction of HBr take place in the presence of peroxide then addition reaction take
place according to Antimarkownikov’s rule. It is also called peroxide effect. The
antimarkovnikov’s rule is applied only in the case of HBr and in the presence of Peroxide.

* Chemical equation from Video

Practice Questions
Example :- 10.4
Intext :- 10.5
Exercise :- 10.7

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