Glucose Structure, open chain, Fisher (Part - 6) - Biomolecules, Chemistry, Class 12 Video Lecture

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talk about the structure of glucose the
glucose looks like this they all carbon
here one carbon two carbon three carbon
Oh carbon five carbon and six carbon one
aldehyde groups and one two three four
five hydroxy - but this structure has
lot of limitations we are not able to
view it properly in three dimensional
because you don't know this is a two
dimensional view then Fischer man came
with this projection and this prediction
is in the use for organic compound only
so this was the structure given this is
a fisherman's structure we'll talk about
these in details and then it was found
that glucose so the properties the
glucose doesn't fit this formula this
structure because they saw that DNP test
and sniff stay there's already test
which was expected for this compound to
work then work properly we will see the
history of that with that this new
cyclic structure was proposed this new
cyclic structure was proposed but this
was confusing if you see you feel that
there is a carbon here there is a carbon
here there is a carbon here right
because there are so many turns this was
confusing so Howard came with this
structure of glucose but still it has
some issues for example this angle was
120 degree which is not correct right
this was more so the angles were not
good and also you cannot actually see a
three-dimensional view properly so this
structure came that
is called the chair structure there are
so many structures for glucose the
history actually behind the structure on
flucos it started with this structure
structure one licinus we are not happy
they came in the structure too but the
chemical reaction to structure to is not
correct
they came with structure tree and if you
see these three structures are all I
mean just for a better depiction it
doesn't
there is no chaining chemical property
with these three structures right they
all same actually but different way of
representing it but these are these are
different the two main three structures
are different one is the open chain one
is cycling right these two there was a
huge jump when we open the chemists move
from structure 2 to 3 but 3 4 & 5 you
see the structures are all same it will
show you how to change or how to give in
a cyclic structure right the howard
structure and or given the hawa
structure at the shade structure we will
discuss the what is is there more of a
representation structure the one which
can represent the glucose in a better
way so this was the history let's talk
about the structure of glucose in detail
before that as I told this has six plus
aldehyde so glucose is aldo hexose X was
y six carbon and aldo why because this
is aldehyde correct also god dextrose so
let's see a little bit of history on how
this structure of glucose was a sign so
up here what was 200 years back Stojko
history was the only chemistry chemist
used to do lot of reactions and then
calculate the molecular mass of the
reactant and the product and with that
they used to find what is the particular
form
reactant so by several reactions the
chemists have found the molecular
formula of glucose to read c6 h-12 o-6
that was the first hint chemist has God
by law of stoichiometry reactions they
found that the molecular formula glucose
is c6h12o6 pay way back right that time
the structure of glucose was not
developed that the science was not
developed not much using stoichiometry
they found that it is c6h12o6 again they
found that when they heated this
particular glucose this the structure is
still unknown to chemists when the
heated is glucose with H I what they got
as n-hexane that is a straight chain
right is an X in the straight chain that
was one to use with that and if you know
this is an aqueous medium actually here
and I'll tell you why you got a straight
chain because in aqueous medium they
will straight chain so with that they
concluded that my glucose shouldn't also
be something like this right this is
this should be the what involve
orientation of the carpet or the
position of carbons in the glucose other
things they are still not sure whether
we should we put oxygen here or here or
here how to put the remaining hydrogen
oxygen they were not very sure but the
kaabah should look something like this
that should be the base or the the
backbone of glucose structure that's
what they found very bad they didn't
know structure just by the
stoichiometric they came from the
molecular formula of glucose and in this
reaction that will glucose react with a
chain across medium admi acts and hexane
is a straight chain so that they
calculate the glucose should look
something like this an oxygen high
during something which has to place so
what next they did more and more
experiments more and more experiments
and they found that the glucose better
act with hydroxy Lamine they form oxide
and they add molecules of hydrogen
cyanide to give sign oh hi try please
note there two different reaction is the
reaction 1 this is reaction 2 so with
this reaction it confirms the presence
of carbonyl in C so when you add in this
2o H you get something like this and
when you add SCN you get something like
that means if you see if you have
something like this you add HC and we
have seen this reaction CN minus will
attack this carbon it will go in this
fashion right negative charge is let die
this edge so with this what you get is C
in here an ovoid shape so we are getting
C n which form when you react with AC
and that means they was early high group
here like so with these reactions they
came to know that my Wilkos should look
something like this this was earlier and
that means there has to be a LD hike row
so till this match the structure was
formed great because react with Sen you
get something like this right that means
these are the high group so till now
they found that the structure is there
to confirm that grid for more
experiments because glucose they found
that it gets oxidized to 6 carbon
carboxylic acid on reaction with while
oxidizing isn't like domine water this
also indicates that there is a carbonyl
toe just a double confirmation correct
so with this also if you see now if you
know that idea till now we have got this
was the structure
correct so this experiment reconfirm
that this is the structure the next
reaction they did was when they did the
acetylation of glucose that is a major
breakthrough no higher with acetic
anhydride it gave glucose Penta a CD
which confirm that they are 5 o h crew
correct and please note that this is
glucose is stable that means is all
these o H group has to be different
carbon so this glucose when it reacts
with acid and I said you can head back
to game 5 this glucose spent acid that
means my current structure was this
right this is something which was the
one now if you see when this is a share
this is for here there are four carbons
area when this reacted with acid
anhydride you get this compound that
means if you see here that means this
this was o s here and this also was
aware so if you replace this these
blocks with Oh H what you get is
something like this
correct okay so with this experiment the
structure of glucose was pretty much
finalized so the thick MS did one more
confirmation to confirm that so when
this glucose was taken which was
structured till now we confirm with
something like this
when this glucose was oxidized with
nitric acid
it gave gluconic acid so it gives Sakura
can see Natalie and gluconic acid also
on oxidation gives cyclic acid this was
you get in both case you take gluconic
acid you oxidize you get cyclic acid you
take glucose oxidase you get cyclic
azmuth means the gluconic acid and the
glucose should have similar structure
right it also indicates that my Oh H
group is the primary group in the nose
so with this the structure of glucose
was pretty much finalized and the
structure was this right please note it
is a two dimensional structure you
cannot actually view the glucose in
three dimensional space because later
the chemists plane that is all three
dimensional scene and there has to be
some structure to explain the
three-dimensional structure right so
what happens is there was a requirement
to represent this glucose in three
dimensional hardwood then came the
fishermen fishermen told that let's do
this a molecule here is my a this my B
is my C and is my D you're weighing it
from this direction then you will see
that B and D is something this is the
one you just put up line parallel to
this angle it is viewing from this time
just draw like plane because this guy is
moving from this point it's let's draw a
line perpendicular to this line so now
if you see that I let this line be the
one which divided this molecule then a
and B something which is going inside
and C I D something just coming outside
correct from C from this guy's
perspective this person is perfect
viewing in this direction let's draw a
line just perpendicular to this line
you get this line and this line in the
break this molecule into two half and
then you see that a and B is something
which is going right a and be something
which is going inside this claim and D
and D see something which is projecting
out correct same thing here so this guy
then you view this this person think
that a and B is going inside and DN C is
coming out if you see a a and B if you
see is going inside the plane and C and
D is coming out he's not able to draw a
line just perpendicular to this line
right so this when you think in this
fashion that means a and B is going
inside and C and D are coming out that
is the Carnation he gave or fisherman
for predicting and this was devised by
Hermann ml in 1891 so it is nothing but
it is a 2d representation of a 3d
organic modulus in 3d organic molecule
you want to represent is a paper and
paper you can represent 2d easily safely
for a 3d organic molecule you want to
have a 2d representation then we use
fisherman prediction please don't is
used only for every component only for
so in this all the bonds are depicted as
horizontal and vertical line so we see
here these are horizontal and horizontal
and vertical lines correct the carbon
change is depicted vertically so this is
the carbon chain is all cross if you see
they all covered so this is my carbon
chain which is depicted vertically
correct
so in this carbon atom is represent by
centre that is crossing the line this
guy the first one is this even by
convention the top and this is C 2 C 3 C
4 C 5 and this becomes C Singh correct
and this is used to differentiate
between l and deep molecules CL in D is
nothing to do with my liber8
rotatory or dexterity this is just
whether my Oh H is on the left so it
will be L or M H 2 sometimes if the if
the compound is in s 2 if that is on the
left that is L if there is on the right
that is d right so this is on right side
and L means left side
please note don't get confused L and D
with label product Li and dick surety
for that we use plus and minus so this
was L n D symbol was given pay before
the Polaroid meter came into picture
where these things are not known the
parameter and the optical activity was
not known but it was known that this
carbon if you see you can have two
different isomers
if you flip H 2 this side o H this side
you get different component we will talk
about this later
don't in confusion this understand is
the horizontal lines projects towards
the viewers these lines all the whole in
two lines they projects towards the
viewer we see C and D is coming towards
a viewer the vertical line
because it's away from the Beavers if
you see so in this case my a and B we
have the vertical mines and it is
projecting away from the Bluebird so
here this carbon of all these carbons
are projecting away from the viewer and
all these HP know which are projecting
towards the viewer correct so it has
vertical mines horizontal line the
cross-section in Holland vertical lines
are my carbons
carvanha generally the vertical line the
first comma in the top most carbon and
the vertical lines is something which is
projecting away from the viewer and the
horizontal lines is something which is
projecting towards up you were this was
a fisherman projection so with this
projection this was the shape of glucose
and this is L or D so when you talk
about D or L will talk about this carbon
the carbon nearness to the last carbon
so in this case is my watch and this on
the left or right obviously the right
since it is on the right right side is T
so this is D glucose actually this is
Libreville whether it is plus or minus
that is something I pull around
polarimeter already tell me so for this
comparative important for Lorena Jupiter
you'll find that this is plus reverse
they will talk about this things later
just understand that where it is deep
revolt because the wedge group is on the
right-hand side and we'll talk about
this which book will discuss this dnl in
detail also in the next few slides you
mean if you do not understand it's okay
next few slides will understand that so
if you talk about the fisherman
projection for other popular organic one
of shock rides then you have gluconic
acid which has this structure and you
have sakura sakura Casson which have
this structure so gluconic acid this is
my first carbon second carbon third
carbon fourth carbon carbon six cup
similarly here also second guessing from
saccharides one carbon two carbon three
carbon low carbon five carbon this is my
sixth Cup
as I promised let us discuss about the D
plus glucose how the name came so if you
see this D before the glucose represents
configuration please note the D
represents configuration whether the Oh
H draw is on the left hand side or right
hand side and plus represents whether it
is the dexstar on entry or lever
auditory nature so you see please note
DN l is not having any relation with
optical activity there is no
relationship between the optical
activity so D can have a plus of optical
activity in some component D can have a
negative optical activity also similarly
L can have a plus optical activity and L
can have - optical activity also this D
and L just depicts the location of
example in this case my OS group is on
the Left fight this is my
d-glyceraldehyde in this case my triple
on the left so this is my L
glyceraldehyde correct this is my L
glyceraldehyde and this my D Kissel in
the end why this is electricity ID
because my OS r upon de l why does
decrease tonight because my OS rwanda
right correct so that was good for
glyceraldehyde but if you see here this
is my glucose res sunni co h bonds right
so here which carbon should i take which
option genetic so in this case we take
the lowest asymmetric carbon so here
this is my lowest asymmetric carbon is
carbon one is common six is my carbon
five so if you see this is my lowest
asymmetric carbon so I'll take this
particular carbon so you take this
particular carbon so in this case Oh H
is all the right right this is D glucose
and now whether it is a plus glucose or
minus glucose that is something we
shared to find experiment li and
experimentally it is seen that this
glucose is plus because it is
Dex to rotatory in nature thank you
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