Organic Chemsitry - Types of Organic Reactions Video Lecture - Class 11

lots of people prefer having margarine
over butter because it has less fat
content not only that but you can also
get vitamins E and a from margarine
what makes margarine a better option
than butter let's find out in today's
episode
hello and welcome it's time for some
crackling chemistry with me the vibrato
Goswami today we will discuss types of
organic reactions in this episode we
will study about two types of attacking
reagents namely nucleophiles and
electrophiles we will also study the
types of organic reactions finally we
will take a look at important questions
and their answers in exam decoded let's
begin with how reactions occur or
reaction mechanism an organic reaction
is believed to take place by the attack
of the reagent on a compound containing
carbon this molecule is also designated
as substrate this leads to the formation
of a number of intermediates these
intermediates finally lead to the
formation of products and byproducts
hope you all have a clear picture of how
reactions take place now let's move to
attacking reagent and their types which
play a major role in any reaction the
attacking reagent is a reactive species
it can be of three types namely
nucleophiles electrophiles
or free radicals
today we will discuss only nucleophiles
and electrophiles let's begin with the
study of nucleophiles nucleophiles are
neutral or negatively charged species
which are capable of donating a pair of
electrons they are denoted by n you
recall that a nucleophile is a nucleus
seeking species it attacks the electron
deficient center of the organic molecule
nucleophiles can be neutral or charged
some examples of neutral species acting
as nucleophiles are water ammonia
alcohols and amines neutral species have
at least one electron pair to donate on
the other hand examples of charged
nucleophiles are chloride ion alkoxide
ion and cyanide
after nucleophiles let's move on to the
second type of attacking agent that is
electrophiles electro files are neutral
or positively charged species which are
capable of accepting a pair of electrons
electro files attack the electron rich
centers of the organic molecule and are
hence electron loving species like
nucleophiles electrophiles can also be
neutral or charged some examples of
neutral electrophiles are boron
trifluoride and aluminum chloride
examples of charged electrophiles are
bromonium ion and nitronium ion can you
name the scientist who introduced the
terms nucleophile and electrophile well
his name is christopher calc in gold
christopher calc in gold introduced the
terms nucleophile and electrophile in
1929 before that the terms get annoyed
and annoyed were used
we must tank Christopher calc in gold
for his valuable contribution to
chemistry but tell me how can a neutral
species like boron trifluoride act as an
electrophile
well as I said before any species that
can attack the negative charge Center is
called an electrophile here
boron trifluoride is electron deficient
since it has only six electrons in its
outermost shell which means the octet is
not complete hence it can easily accept
electrons and can act as an electrophile
the classification of organic reactions
is based on attacking species that is
nucleophiles or electrophiles how is
this classification done let me tell you
organic reactions can be classified into
four types that is substitution
reactions addition reactions elimination
reactions and rearrangement reactions
let's begin with substitution reactions
as the name suggests it is the reaction
in which an atom or group of atoms in a
molecule is replaced or substituted by
different atom or group of atoms based
on the attacking species the
substitution reactions can be further
classified as nucleophilic substitution
and electrophilic substitution reactions
in a nucleophilic substitution reaction
an atom or a group of atoms in a
molecule is replaced by a nucleophile
let's take a look at this reaction when
bromoethane is reacted with sodium
hydroxide ethanol and sodium bromide are
formed here bromo group is replaced by
the nucleophile hydroxide ion now let's
move on to another type of substitution
reaction the electrophilic substitution
reaction in an electrophilic
substitution reaction an electrophile
attacks the substrate substituting one
of the group's an example of an
electrophilic substitution is nitration
of benzene in this reaction the
electrophile is nitronium ion it is
generated by the reaction of
concentrated sulfuric acid and nitric
acid nitronium ion then reacts with
benzene ring to produce nitro benzene
after substitution reactions let's move
on to addition reactions addition
reactions are those reactions in which
two molecules react to form a single
product one important point here is that
the addition product should have all the
atoms of the combining units well it's
time for me to take a short break but
here is a question to get your mind
racing classify the following reagents
as electrophiles and nucleophiles a
water be aluminum chloride C acetate ion
D bromonium ion if you need help on this
one
you can log on to www.nasa.gov
welcome back I am do brother Goswami and
you are watching chemistry 11 before the
break I had asked you to classify the
following reagents as electrophiles and
nucleophiles a water B aluminum chloride
C acetate ion D bromonium ion and the
answer is water is a neutral nucleophile
an acetate ion is a charged nucleophile
aluminum chloride is a neutral
electrophile and bromonium ions is a
charged electrophile remember in the
beginning of the show I told you that
margarine is healthier than butter it is
because margarine contains more
unsaturated fatty acids butter on the
other hand is a saturated fatty acid
therefore butter leads to increase in
cholesterol and hence is not good for
health the conversion of unsaturated
fatty acids to saturated fatty acids is
an addition reaction let us now study
addition reactions you must remember
addition reactions are limited to
chemical compounds that have multiple
bonds like carbon-carbon double bonds or
carbon-carbon triple bonds or molecules
with double bonds between carbon and a
hetero atom like oxygen addition
reactions are divided into two types
again based on the attacking species
being added there are nucleophilic
addition reactions and electrophilic
addition reaction
and naturally the additional reaction
carried out by the nucleophile as the
attacking agent is called nucleophilic
addition reaction the formation of sino
hydron from the reaction of acetaldehyde
with hydrogen cyanide is an example of
nucleophilic addition reaction so what
are electrophilic addition reactions in
simple terms
those addition reactions in which the
attacking species is an electrophile is
called electrophilic addition reactions
let us understand electrophilic addition
reactions better with this example the
addition of bromine to it in to form one
to dye bromo ethane is an example of
electrophilic addition reaction now
let's do an experiment you can even do
this experiment in your school
laboratory the importance of this
reaction is that this test is used to
identify the presence of unsaturation in
a compound we take 3 to 4 ml alkene in
about 2 ml carbon tetrachloride
we add 1 ml of bromine water drop by
drop we see that the yellow color of
bromine water disappears this shows that
the solution contains carbon-carbon
double or carbon-carbon triple bonds if
the yellow color does not decolorize
then the solution does not contain
carbon-carbon double or carbon-carbon
triple bonds
moving on let's see how we classify
elimination reactions an elimination
reaction as the name suggests leads to
the removal of groups of atoms or
molecule at this point we have a student
who is calling in with a query let's
here our young callers question hello
sir my name is Samuel I just wanted to
know whether the atoms eliminated in an
elimination reaction are present on the
same atom or on the different atoms of
the substance that's a good question
it can happen either way in elimination
reactions the two atoms a group of atoms
may be removed from the same or from
different atoms of the substance let me
clear this concept with an example which
is also important from your examination
point of view take a look at the
reaction shown on your screen the
formation of carbon is an example of
elimination reaction in which two atoms
are lost from the same atom on the other
hand the D hydro halogenation reaction
is an example of elimination reaction in
which the loss of two atoms or groups
occur from two different atoms of the
substance in this reaction hydrogen and
bromine are eliminated forming an alkene
as I told you earlier organic compounds
typically undergo four types of
reactions the substitution reaction
addition reaction elimination reaction
and the rearrangement reaction so what
are rearrangement reactions in a
rearrangement reaction the migration of
atoms or groups of atoms
takes place from one position to another
within the molecule under suitable
conditions take a look at the reaction
shown on your screen the conversion of
n-butane to isobutane in the presence of
aluminum chloride is an example of
rearrangement
well with that we have reached the end
of the theory for today it's time for me
to take a short break now
so why don't you refresh yourselves for
what's up ahead that's right get ready
for exam decoded coming up right after
the break
welcome back to the fascinating world of
organic chemistry
I am the Oh Bravo and today we are
discussing organic reactions here is a
quick revision of what we have learned
so far in this episode we learned that
nucleophiles are the neutral or
negatively charged species which are
capable of donating a pair of electrons
electrophiles
a neutral or positively charged species
which are capable of accepting a pair of
electrons from the substrate molecule
the reactions in which an atom or group
of atoms in a molecule is replaced or
substituted by different atoms or group
of atoms are called substitution
reaction reactions in which two
molecules react to form a single product
are called addition reactions now that
we know our topic let's not waste any
more time on two exam decoded
welcome to exam decoded your very own
vault of exam tips and guidelines to
secure top marks if you would like to
assess how your preparation is going
let's do a trial run with a rapid-fire
round this is a round of 5 questions for
one mark gauge you will get just 5
seconds to answer each question then we
will total up and interpret your final
scores let's get started with the first
question
conversion of n-butane to isobutane is
an example of which type of reaction
Bridget edition which substitution see
elimination each rearrangement if your
answer is ding give yourself one mark
conversion of n-butane to isobutane is
an example of a rearrangement reaction
next question a plus B going to KB is
which type of reaction addition
substitution see elimination G
rearrangement
absolutely right it's a addition
reaction here is the third question
which one of the following represents an
example of a charged electrophile a no.2
plus B bf3 c BR plus these both a and C
the answer is question number four is
nitration of benzene is an example of
which type of reaction a substitution
we edition see a rearrangement the
elimination the correct answer is a
substitution reaction your fifth
question is aluminum chloride is an
example of a neutral electrophilic
reagent true or false
the answer is filled with that we have
come to the end of the rapid-fire round
now let's add up your scores and see how
you have fared by 1/5 qualifies you as a
high-flyer so well done four or three on
five makes you an achiever this means
you are on the right path and you have
the potential to achieve even more less
than three makes you a learner who needs
to put in some more work so log onto
www.koco.com astray which can either
wait age of seven marks and since your
chemistry paper is for a total of
seventy marks it is critical from the
examination point of view so be prepared
to face short answer type questions for
two to three marks each these will
usually test your knowledge ability well
now that you know what questions you may
be asked in your exams let's see how you
should answer them here is an example
identify the various types of chemical
reactions in the following reactions the
first reaction is ethene reacts with
bromine to give one to dyed romo attend
second reaction is ammonium cyanate
converts to urea this question can come
in your exams for two marks and this is
how you should answer it look at the
first reaction
you can see that two molecules Ethan and
bromine combine to form a single product
one to die bromo Ethan so it is an
addition reaction further to identify
the type of addition reaction we see
that the reaction is carried out by an
electrophile which is bromonium ion
these are the characteristics of an
electrophilic addition reaction writing
the correct name of the reaction will
fetch you one mark in the second
reaction there is no addition or removal
of any reagent thus it is neither
addition nor substitution reaction we
observe that there is a rearrangement of
atoms which has taken place these are
the characteristics of a rearrangement
to reaction writing the correct name of
the reaction will fetch you one mark
today's show has been all about organic
reactions we have seen how everything
around us is subject to variations and
transformations so I will leave you with
a thought inspired by these phenomena we
have learnt about electrophiles
can you tell me what are super electro
files keep thinking or log on to
www.wymt.com
you