Preparation from Alkenes (Part - 12) - Haloalkanes & Haloarenes, Chemistry, Class 12 Video Lecture

hello friends this video on haloalkanes
in Halawa is part 12 is brought to you
by exam fear calm no more free from exam
now let's understand the progression
from alkenes using hydrogen halide so
the reaction is typically I have alkenes
then I use hydrogen halides
and what you get is haloalkanes
is the reaction and this is
electrophilic addition me right here a
leg through building addition I will
explain you why it is electrophilic
addition alkyne Ashley see if you see
something like this right double bond so
in this you add a hydrogen alight so
double bond breaks and addition happens
here so you get something like this H
then you exit so typical reaction this
is an in this case if you see my h plus
and ex minus my electrophile is getting
a little the first attack is my
electrophile here it is h plus and ex
minus if you see this guy is the one
starts first and this follows mark on
akamaru
that the stable carbo cations form in
this case H I is fastest we have seen a
chai is very reactive and then here H F
is slowest why because the fluorine the
bond length is less right it is
difficult to break
hie bond length is more easy to break
hey base my size let's see this reaction
example I haves CH 3 CH double bond CH 2
I react with H I so what will happen is
this bond will break this can break
either in this direction of insurrection
it breaks in this direction let's ease
both the possibility it takes in this
direction in terms what in lapidus CH 3
CH ch2 this will get minus VJ plus plus
and if it breaks in this direction later
person decides so what will get in here
ch3 minus n CH 2 correct now they told
the first guy to attack is edge let's
attach h plus here so this will become
ch3 here also a - h plus shouldn't
become ch2 so out of these two which one
is more reactive which one is more
stable
obviously this right because this is
secondary carbo cation so this is more
stable this is the major product correct
so since this is more stable carbo
cation so now here I can add BR this is
my major product BR minus so this charge
will go in this will be minor and this
will be million all right so let's see
the reaction mechanism actually here so
the reaction mechanism is really simple
actually so let's suppose I have CH 3 CH
double bond CH 2 so I have got h bi bi
will get slightly negative charge they
coded slightly polar isn't it rightly
positive sharp so this double bond will
attack this much here so with this what
you get is CH 3 CH in the Lord
eh - sorry
ch3 plus you get here right because this
will become a stable carbo cation this
is what you get right this will attack
here correct and then my BR - will
attack this sorry this bond would break
into positive and negative right she
will be negative and this will be
positive this is how it is break and on
this negative - this will be dashed
right so H+ will be attacks it from CS 3
and this negative charge evil this Idol
bit is gone will break in this scale the
negative is the only positive and on
this this attached here and this becomes
question or you can assume this faith
this bond breaks you will get ch3 here
and you get h+ here why have you got
this bond broke like this bond grow and
this H bar attached to this carbon and
you got plus here correct so this is
what we get and on this now BR minus
will get attached this is the reaction
mechanism for this reaction and please
note this is using Marconi cockle and we
have seen that with HBR only with HBR if
you use peroxide then we have anti
mechanical rule where you get this as a
major product why because it it goes
from free radical reaction you have seen
the example just two or three slides
back
now let us talk about hair regeneration
so I have a alkene in this case if I
have alkene they want to add a halogen
if I add some illusion in presence of I
do in the presence of CCL 4 so what you
get is 1 X here 1 X here is what is it
similarly if you want to add for example
in 0 I mean X can be anything fluorine
chlorine bromine anything right for
example I can take is I have et in this
let me add bromine in presence of CCL 4
I get here
via H H and devotion this is what we go
so let's see the reaction mechanism for
this I have this so in this case let me
see this h h so bromine will break
actually it has slightly positive n it
slightly negative shock so this bond
will break and what will form is this
bromine will get attached here with
positive charge here so what you get
here is ch2 ch2 here with a constitution
and now this pr- will attack it so what
you get is ch2 they are ch2 that's what
you get right similarly we can have one
more reaction similar to this I have
this cyclohexene in this if I I'd be our
business of CCL 4 so you get this sorry
I mean here and you get no me this is
one to die bromo cyclohexane correct one
to dive mo satellites
this is cyclohexene and this is also
example of electrophilic addition
because the first thing that is getting
reacted is BR plus it is electrophilic
addition reaction
let's take some numerical solid write
the product so in this case the moment
you add hbr so since you're not using
peroxide you follow
Marconi cough rules which one is more
stable carbo cation this guy is plus
charge it is a more stable carbocation
correct instead of this why because this
carbon is secondary carbon right to
govern - this is only trying be carbon
so this gets a plus charge that is
better so that means the gauge /aa that
will be I will attack in this game so
the product has to be c BR h and ch3
this will be the product using a Marconi
Kapoor logs why because H plus BR -
right h plus will first attacked this
way so that you get the more stable
carbo cation and then we are - will
attract the comical correct this is also
electrophilic addition reaction let's
say this game SC L so here also first H
will attack so I should attack this
position of this position so if it
attack this position you get more stable
carbo cation
correct will get this carbo cation and
this carbon is sig into gamma if it
attacks this carbon it will get this
come over time which is a primary carbon
and so H at a time this carbon so that
you get secondary carbo cation so with
this you get CH 3 CH 2 CH CL correct
because let's attack this so the
intermediate product which you got in
this first let me write here CH 3 CH CH
1 over time and that is the intermediate
product Oh God then CL minus attacked
this we shouldn't get this now the same
reaction am a similar reactions with a
better sign the balance of it this
precise no it goes for anti-masonic true
because we have free radical reaction
happening here so using
marconi cough BR should come here
so using anti markovnikov BR ship come
that will be the photon just by that you
can tell or I can give you the
explanation now this is what you get
why because hbr will be now BR dot NH
dot that's further break you get BR free
radical so BR free radical is the one
which will attack first
right and so be Fe radical will attack
this position because this is the more
stable compound and then here ash so
it's n time or conical rule then you
have HBR reaction in presence of hair
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