so we looked at IR spectroscopy which, once again, spectroscopy is the study of the
so we looked at IR spectroscopy which, once again, spectroscopy is the study of the

interaction of light and matter and we know that we can use that to identify
interaction of light and matter and we know that we can use that to identify

what kind of functional groups might or might not be on a molecule, but that's
what kind of functional groups might or might not be on a molecule, but that's

not going to be good enough because if we want to do modern synthetic chemistry
not going to be good enough because if we want to do modern synthetic chemistry

which is very complicated, we want to try to be able to build any molecule that we
which is very complicated, we want to try to be able to build any molecule that we

can think up. when we do chemistry if we do a multistep synthesis we have to be
can think up. when we do chemistry if we do a multistep synthesis we have to be

sure that every step along the way and then especially on our final product we
sure that every step along the way and then especially on our final product we

need to know exactly what molecule we have, all of the connectivity, all of the
need to know exactly what molecule we have, all of the connectivity, all of the

stereochemistry, if we're going to make something complicated like let's say
stereochemistry, if we're going to make something complicated like let's say

this molecule which is called xerantholide, we need a spectroscopic
this molecule which is called xerantholide, we need a spectroscopic

technique that is gonna, we're going to be able to get information on this, on
technique that is gonna, we're going to be able to get information on this, on

what we think is that compound and be able to definitively say: yes it is that
what we think is that compound and be able to definitively say: yes it is that

molecule down to every tiny detail and that method is nuclear magnetic
molecule down to every tiny detail and that method is nuclear magnetic

resonance spectroscopy or NMR spectroscopy. now there's a few different
resonance spectroscopy or NMR spectroscopy. now there's a few different

forms
forms

we're gonna look at proton NMR and so the way NMR works, it
we're gonna look at proton NMR and so the way NMR works, it

is a form of spectroscopy so it is the study of interaction of light matter but
is a form of spectroscopy so it is the study of interaction of light matter but

there's a twist here, and it is the case that certain atomic nuclei
there's a twist here, and it is the case that certain atomic nuclei

exhibit nuclear spin and we can take advantage of that nuclear spin by
exhibit nuclear spin and we can take advantage of that nuclear spin by

subjecting a molecule to an external magnetic field and when
subjecting a molecule to an external magnetic field and when

we do that we're going to be able to get some very interesting data, when
we do that we're going to be able to get some very interesting data, when

we then get spectroscopic data from it so that is we induce a magnetic field
we then get spectroscopic data from it so that is we induce a magnetic field

and then we irradiate with light and we gather information about how
and then we irradiate with light and we gather information about how

the light interacts with that compound so without getting too into the physics
the light interacts with that compound so without getting too into the physics

of it all
of it all

we're just understand we're looking at proton NMR involving protium, these are
we're just understand we're looking at proton NMR involving protium, these are

protium nuclei, so protium, which is a hydrogen isotope of mass one as opposed to
protium nuclei, so protium, which is a hydrogen isotope of mass one as opposed to

deuterium and tritium and what happens is we're going to be able to
deuterium and tritium and what happens is we're going to be able to

radiate this with light and then get back information that tells us
radiate this with light and then get back information that tells us

the precise chemical
the precise chemical

environment of every single proton in this molecule and we can use that information
environment of every single proton in this molecule and we can use that information

to discern the precise structure of the molecule so let's take a look at one of
to discern the precise structure of the molecule so let's take a look at one of

these spectra and talk about how we can interpret them
these spectra and talk about how we can interpret them

i've drawn a sample NMR spectrum and we're gonna talk about the three main pieces of data that we are
i've drawn a sample NMR spectrum and we're gonna talk about the three main pieces of data that we are

going to try to gleam from any NMR spectrum. so once again we're doing, this
going to try to gleam from any NMR spectrum. so once again we're doing, this

is going to be very simple example, we're not going to get too in depth but just
is going to be very simple example, we're not going to get too in depth but just

the very basic way, what can we get from an NMR spectrum so first of all what is going
the very basic way, what can we get from an NMR spectrum so first of all what is going

on here, so right here we have a reference peak this is called TMS that's
on here, so right here we have a reference peak this is called TMS that's

tetramethyl silane, and then everything else is given in parts per
tetramethyl silane, and then everything else is given in parts per

million in terms of where it stands in reference to the TMS. this is a reference
million in terms of where it stands in reference to the TMS. this is a reference

peak so that's not data that's going to be on any spectrum and then this stuff
peak so that's not data that's going to be on any spectrum and then this stuff

this is the data. ok so how is this data how are we interpreting these peaks, these
this is the data. ok so how is this data how are we interpreting these peaks, these

resonances? well there's three things that we want to take into account for
resonances? well there's three things that we want to take into account for

any resonance on a spectrum. that is going to be the chemical shift, the
any resonance on a spectrum. that is going to be the chemical shift, the

integration, and the splitting. so what do these three things mean? let's talk about them
integration, and the splitting. so what do these three things mean? let's talk about them

one at a time. so chemical shift all chemical shift means is where is it
one at a time. so chemical shift all chemical shift means is where is it

where is it on the spectrum, is it more downfield or is it more upfield. now what
where is it on the spectrum, is it more downfield or is it more upfield. now what

this has to do with is it tells us about the chemical environment of a particular
this has to do with is it tells us about the chemical environment of a particular

proton. remember that these are protons that are generating these resonances so
proton. remember that these are protons that are generating these resonances so

in a molecule anywhere where there is a hydrogen atom you are getting some
in a molecule anywhere where there is a hydrogen atom you are getting some

information about the chemical environment of that hydrogen atom or
information about the chemical environment of that hydrogen atom or

that proton, so what happens is the closer that that proton is to some
that proton, so what happens is the closer that that proton is to some

electronegative element the electronegative atom is going to have a
electronegative element the electronegative atom is going to have a

deshielding effect because of its electronegativity it is going to
deshielding effect because of its electronegativity it is going to

withdraw the electron density of the proton away from the nucleus which we
withdraw the electron density of the proton away from the nucleus which we

call a deshielding effect, because the electrons are moving away from the
call a deshielding effect, because the electrons are moving away from the

nucleus and then that will cause that signal to be more downfield so more
nucleus and then that will cause that signal to be more downfield so more

downfield means closer to electronegative atoms
downfield means closer to electronegative atoms

and this means upfield means farther away from electronegative elements so number
and this means upfield means farther away from electronegative elements so number

one the chemical shift is telling us about the chemical environment that
one the chemical shift is telling us about the chemical environment that

means where is it on the spectrum. this way is closer to electronegative elements
means where is it on the spectrum. this way is closer to electronegative elements

this is further away from electronegative elements. number two is
this is further away from electronegative elements. number two is

integration so let's say that we have some chemically equivalent protons, that
integration so let's say that we have some chemically equivalent protons, that

might be three protons on the same methyl group as they're spinning around
might be three protons on the same methyl group as they're spinning around

they see the same thing as they look down the rest of the molecule, they are
they see the same thing as they look down the rest of the molecule, they are

experiencing an identical chemical environment so what ends up happening is
experiencing an identical chemical environment so what ends up happening is

let's say we have one proton on that methyl group that generates this
let's say we have one proton on that methyl group that generates this

resonance, generates this information right here, then that second proton also
resonance, generates this information right here, then that second proton also

generates the same resonance so that just enhances this peak and it will get
generates the same resonance so that just enhances this peak and it will get

bigger and then that third proton also generates the exact same resonance, or
bigger and then that third proton also generates the exact same resonance, or

the exact same data so that too will cause this to grow and what that means
the exact same data so that too will cause this to grow and what that means

is this is an integration, the integration literally means the area
is this is an integration, the integration literally means the area

under the curve so NMR spectra don't look exactly like this is an
under the curve so NMR spectra don't look exactly like this is an

oversimplified view of it but whatever data is happening under that peak
oversimplified view of it but whatever data is happening under that peak

the integration means the area under the curve so we can just consider it to be
the integration means the area under the curve so we can just consider it to be

kind of how tall is it or how big is the resonance and so that's the second bit
kind of how tall is it or how big is the resonance and so that's the second bit

of information is the integration, the integration is telling us how many
of information is the integration, the integration is telling us how many

chemically equivalent protons are generating that peak so if this is
chemically equivalent protons are generating that peak so if this is

integrated to 2, and this is integrated to 3, then what we're saying is that two
integrated to 2, and this is integrated to 3, then what we're saying is that two

chemically equivalent protons are making that one and three are making that one
chemically equivalent protons are making that one and three are making that one

so that's integration, that's saying how many protons are generating
so that's integration, that's saying how many protons are generating

that peak. now the last thing we want to talk about is splitting and so
that peak. now the last thing we want to talk about is splitting and so

chemically equivalent protons will generate the same resonance but then
chemically equivalent protons will generate the same resonance but then

that resonance will be split into a certain number of smaller peaks
that resonance will be split into a certain number of smaller peaks

depending on neighboring protons and so what we want to understand is
depending on neighboring protons and so what we want to understand is

so this is about neighboring protons and this is the n + 1 rule and so
so this is about neighboring protons and this is the n + 1 rule and so

basically what you're saying is let's say we have a hydrogen that is generating some
basically what you're saying is let's say we have a hydrogen that is generating some

resonance it's generating some resonance but then if there is a neighboring
resonance it's generating some resonance but then if there is a neighboring

proton that acts like a little magnet, let's see we're looking at a proton
proton that acts like a little magnet, let's see we're looking at a proton

one carbon over and that proton will split this one into two resonances
one carbon over and that proton will split this one into two resonances

now let's say that there's another, there's a second neighboring proton that
now let's say that there's another, there's a second neighboring proton that

will split this into two resonances and this into two resonances so we'll have
will split this into two resonances and this into two resonances so we'll have

an overlap there and that one will be more intense this middle one will be
an overlap there and that one will be more intense this middle one will be

more intense and so that's why we see something like this we have the middle
more intense and so that's why we see something like this we have the middle

one is the longest but at any rate we are seeing that an individual resonance
one is the longest but at any rate we are seeing that an individual resonance

that is generated by one proton will be split into a series of smaller
that is generated by one proton will be split into a series of smaller

peaks by neighboring protons and so specifically it will be split into n +1
peaks by neighboring protons and so specifically it will be split into n +1

peaks where n is the number of neighboring protons so if we have some
peaks where n is the number of neighboring protons so if we have some

chemically equivalent protons with let's say two protons next door
chemically equivalent protons with let's say two protons next door

it will be split into three peaks or a triplet so this is called a triplet this
it will be split into three peaks or a triplet so this is called a triplet this

would be called a quartet, we could have a singlet, we could have a doublet, so
would be called a quartet, we could have a singlet, we could have a doublet, so

that's splitting. that is telling us the number of of neighboring protons so
that's splitting. that is telling us the number of of neighboring protons so

that's the three bit of data so now let's let's look at the structure of
that's the three bit of data so now let's let's look at the structure of

what this actually is, what this actually is is bromoethane and lets assign the
what this actually is, what this actually is is bromoethane and lets assign the

peaks so what we need to understand is that we have two different, we have two
peaks so what we need to understand is that we have two different, we have two

different resonances to expect because these two protons are chemically
different resonances to expect because these two protons are chemically

equivalent, usually the protons on the same carbon are chemically equivalent
equivalent, usually the protons on the same carbon are chemically equivalent

and then we have three that are chemically equivalent over
and then we have three that are chemically equivalent over

here so let's look at this one first we're saying that these are three of
here so let's look at this one first we're saying that these are three of

them so we better have integrated to 3 so it's probably gonna be this peak. in
them so we better have integrated to 3 so it's probably gonna be this peak. in

addition it's further away from the bromine so it should be more upfield and
addition it's further away from the bromine so it should be more upfield and

then
then

it's going to be split by the two neighboring protons into a triplet
it's going to be split by the two neighboring protons into a triplet

because 2 + 1 is a triplet so we have a triplet that is integrated to 3 that is
because 2 + 1 is a triplet so we have a triplet that is integrated to 3 that is

more upfield so this peak certainly corresponds to B. then looking at A, we're
more upfield so this peak certainly corresponds to B. then looking at A, we're

saying that we need to look for a peak that number one is integrated to 2 because
saying that we need to look for a peak that number one is integrated to 2 because

there are two protons, also it should be further upfield because it's closer to
there are two protons, also it should be further upfield because it's closer to

the bromine atom, the bromine atom is going to deshield those protons so that's
the bromine atom, the bromine atom is going to deshield those protons so that's

further upfield and then additionally the three neighboring protons 3 + 1 is 4
further upfield and then additionally the three neighboring protons 3 + 1 is 4

it should be split into a quartet by those neighboring protons so this
it should be split into a quartet by those neighboring protons so this

certainly is going to be A. so just to reiterate we have chemical shift: where
certainly is going to be A. so just to reiterate we have chemical shift: where

is it sitting on the spectrum, we have integration: how tall is it, more or less
is it sitting on the spectrum, we have integration: how tall is it, more or less

which refers to the number of protons that are generating that resonance and
which refers to the number of protons that are generating that resonance and

then the splitting pattern which tells us how many neighboring protons there are.
then the splitting pattern which tells us how many neighboring protons there are.

ok let's look at one more simple spectrum to make sure that we can we can
ok let's look at one more simple spectrum to make sure that we can we can

assign these NMR spectra. so let's say we're looking at this compound and we
assign these NMR spectra. so let's say we're looking at this compound and we

want to match the protons to the peaks that they correspond to. this
want to match the protons to the peaks that they correspond to. this

is probably going to be something you'll do in any organic chemistry course you'll be
is probably going to be something you'll do in any organic chemistry course you'll be

given a compound and a spectrum and the problem will say match the protons
given a compound and a spectrum and the problem will say match the protons

to the peaks they correspond to. so first of all let's make sure we understand
to the peaks they correspond to. so first of all let's make sure we understand

where the protons are, so we've got three there we've got two there
where the protons are, so we've got three there we've got two there

and we've got three there. we definitely have to be able to do that otherwise this is
and we've got three there. we definitely have to be able to do that otherwise this is

going to be extremely difficult. now we know that for the most part at least at
going to be extremely difficult. now we know that for the most part at least at

this early stage of analyzing NMR spectra let's just say that all the protons on
this early stage of analyzing NMR spectra let's just say that all the protons on

an individual carbon are gonna be chemically equivalent because let's see
an individual carbon are gonna be chemically equivalent because let's see

we've got these three protons on this methyl as this bond is rotating
we've got these three protons on this methyl as this bond is rotating

there's no there's no spatial differentiation it doesn't matter if one's
there's no there's no spatial differentiation it doesn't matter if one's

down or up or whatever
down or up or whatever

as they spin around like you know like a top they're all seeing the
as they spin around like you know like a top they're all seeing the

same chemical environment
same chemical environment

so these are all the same, let's call them A, these two of the same
so these are all the same, let's call them A, these two of the same

let's call them B, these three are the same let's call them C. now one
let's call them B, these three are the same let's call them C. now one

very good method, either we could just try to assign straight off the bat but
very good method, either we could just try to assign straight off the bat but

first just to be a little more thorough let's make predictions about what we
first just to be a little more thorough let's make predictions about what we

could expect from each resonance, so looking at A first we know that this is
could expect from each resonance, so looking at A first we know that this is

going to be integrated to 3, we know it's going to be integrated to three
going to be integrated to 3, we know it's going to be integrated to three

because there are three protons ok then let's talk about splitting there are no
because there are three protons ok then let's talk about splitting there are no

neighboring hydrogens there are no neighboring hydrogen so it will not be
neighboring hydrogens there are no neighboring hydrogen so it will not be

split at all, we are expecting a singlet here and then lastly this we expect to
split at all, we are expecting a singlet here and then lastly this we expect to

be relatively upfield because it is near a carbonyl carbon. now if we want to be
be relatively upfield because it is near a carbonyl carbon. now if we want to be

very specific with our predictions we could consult a table that would tell us
very specific with our predictions we could consult a table that would tell us

the exact ppm to expect for hydrogens next to a given functional group
the exact ppm to expect for hydrogens next to a given functional group

whatever it is so we may not even really need to though because we have plenty of
whatever it is so we may not even really need to though because we have plenty of

information here, this is a very simple molecule there's only three peaks so
information here, this is a very simple molecule there's only three peaks so

this is going to be enough. a 3H singlet that is relatively upfield
this is going to be enough. a 3H singlet that is relatively upfield

that's plenty of information then over here we know that there's two hydrogens
that's plenty of information then over here we know that there's two hydrogens

so we expect that resonance is gonna be integrated to 2 and then we expect
so we expect that resonance is gonna be integrated to 2 and then we expect

it to be split into a quartet because there are three neighboring hydrogens so
it to be split into a quartet because there are three neighboring hydrogens so

here's the hydrogens we're talking about, the neighboring ones are
here's the hydrogens we're talking about, the neighboring ones are

right here, there's three of them and so 3 + 1 gives us 4, a quartet. there are no
right here, there's three of them and so 3 + 1 gives us 4, a quartet. there are no

hydrogens over here, that's an oxygen so a 2H quartet that should be again
hydrogens over here, that's an oxygen so a 2H quartet that should be again

relatively upfield because these are adjacent to an oxygen atom, an oxygen
relatively upfield because these are adjacent to an oxygen atom, an oxygen

atom is very electronegative it is as a lot of electron-withdrawing capability
atom is very electronegative it is as a lot of electron-withdrawing capability

so this should be relatively deshielded and relatively upfield protons or the
so this should be relatively deshielded and relatively upfield protons or the

resonance that corresponds to those protons. then lastly right here we've
resonance that corresponds to those protons. then lastly right here we've

got three chemically equivalent protons so we should expect the peak to be integrated
got three chemically equivalent protons so we should expect the peak to be integrated

to 3, we should expect that it is split into a triplet because we have two
to 3, we should expect that it is split into a triplet because we have two

neighboring hydrogens so
neighboring hydrogens so

n is 2, n + 1 = 3, this resonance should be split into three smaller peaks or a
n is 2, n + 1 = 3, this resonance should be split into three smaller peaks or a

triplet and then we should expect that is it is relatively, you know what I
triplet and then we should expect that is it is relatively, you know what I

think I mixed up, what I meant was downfield here and this should be
think I mixed up, what I meant was downfield here and this should be

relatively upfield because it is not near any electron withdrawing
relatively upfield because it is not near any electron withdrawing

group so it is relatively shielded it will stay relatively upfield so we have
group so it is relatively shielded it will stay relatively upfield so we have

a 3H triplet upfield so now this is going to be very easy to assign
a 3H triplet upfield so now this is going to be very easy to assign

because so let's say here we have a 3H triplet upfield well this is integrated
because so let's say here we have a 3H triplet upfield well this is integrated

to 3, it is a triplet, and it is upfield so this is certainly resonance C. here we
to 3, it is a triplet, and it is upfield so this is certainly resonance C. here we

have a 2H quartet downfield so here is, it's integrated to 2, it's a quartet, it's
have a 2H quartet downfield so here is, it's integrated to 2, it's a quartet, it's

downfield, that's gotta be B. and then we have a we have a 3H singlet that
downfield, that's gotta be B. and then we have a we have a 3H singlet that

may or may not be downfield, it's right there in the middle and so that is
may or may not be downfield, it's right there in the middle and so that is

certainly going to be peak A. so once again when we are looking at a molecule and
certainly going to be peak A. so once again when we are looking at a molecule and

you're trying to assign resonances to the protons that they correspond to
you're trying to assign resonances to the protons that they correspond to

we're going to be looking at three things, were looking at chemical shift
we're going to be looking at three things, were looking at chemical shift

we're looking integration, and we're looking at splitting, and all we need to
we're looking integration, and we're looking at splitting, and all we need to

do is get enough data to be able to assign those peaks accordingly.
do is get enough data to be able to assign those peaks accordingly.

thanks for watching guys, subscribe to my channel for more tutorials and as always
thanks for watching guys, subscribe to my channel for more tutorials and as always

feel free to email me
feel free to email me