NMR

2. • Nuclear magnetic resonance spectroscopy
most commonly known as NMR spectroscopy
is the name given to the technique which
exploits the magnetic properties of certain
nuclei. This phenomenon and its origins are
detailed in a separate section on Nuclear
magnetic resonance
• It deals with the measurement of abs of r.f.
radiation in 4-9000 MHz by a subs held in mag
field.
• When placed in a magnetic field, NMR active
nuclei (such as 1H or 13C) absorb at a
frequency characteristic of the isotope. The
resonant frequency, energy of the absorption
and the intensity of the signal are proportional
to the strength of the magnetic field.

3. • NMR spectra is a plot of chemical shift
in , δ unit vs. intensity of peak.
• E.g. toluene:-proton NMR spectrum
shows two groups of hydrogen atoms
that is methyl hydrogen atom and ring
hydrogen hence two signal appears in
the spectrum corresponding to two
different chemical and magnetic
environment.

4. • APPLICATIONS:
• Useful to understand size and shape of
the molecule..
• NMR became imp tool for elucidation of
molecular structure including
stereochemistry & confirmation.
• Also use for identification & testing of
pharmaceutical analysis.
• Also use for qualitative and quantitative
work in pharmaceutical industry.
• To study the magnetic properties of
various nuclei.

5. THEORY AND PRINCIPLE:
• SPINNING NUCLEUS:
• Nucleus of proton behave as a tiny
spinning bar magnet because it
posses both electric charge and
mechanical spin any spinning
charged body generates a magnetic
field.

6. EFFECT OF EXTERNAL
MAGNETIC FIELD:
• In the presence of an
external magnetic field
(B0), two spin states exist,
+1/2 and -1/2.
• The magnetic moment of
the lower energy +1/2
state is alligned with the
external field, but that of
the higher energy -1/2
spin state is opposed to
the external field. Note
that the arrow
representing the external
field points North.

7. PRECESSIONAL MOTION:
• Proton is a spinning magnet not it can 0nly
align or oppose the applied field but also it will
move in a characteristic way under the effect of
external magnetic field.
• E.g. Spinning top along with spinning motion
the top will also perform slower waltz like
motion in which the spinning axis of top moves
slowly around the vertical.
• This is a precessional motion and the top is said
to be precessing around the vertical axis of the
earths gravitational field.

9. PRECESSIONAL FREQUENCY
• The spinning frequency of nucleus does not
change but speed of precession changes.
• Precessional frequency (V ) is directly proportional to
Strength of the External field (Bo)
• In an applied magnetic field like the proton
precess at a frequency V which is proportional
to the strength of applied field.
V =  Bo
2

10. • Bo is strength of external magnetic field
experienced by proton.
•  = Magnetogyric ratio (Ratio between
nuclear magnetic moment μ and nuclear
angular momentum I)
•  = 2μ
hI

11. • So V = 2μ Bo
hI 2
= μ Bo
hI
μ = 1.41 * 10-30 J/G
Bo= 14000 G
h = 6.626 * 10-34 J sec
I = ½
Protons will precess 60 million times per sec in
14000 G mag field.
So proton will absorb at frequency of 60 MHz when
14000 Gauss external field is applied.

12. • Similarly NMR frequency for various
other nuclei can be calculated taking
their respective μ values .
• E.g 13C absorb at 15 MHz .
• 19 F Absorb at 56 MHz when
14000 gauss external magnetic field
is applied.

13. • ENERGY TRANSITION:
• A proton in an external magnetic field of 1.4
tesla will precess at a frequency of 60 MHz
and is capable of taking one of two
orientation with respect to the axis of
external field aligned or opposed i.e. parallel
or anti parallel.
• If proton is precessing in aligned orientation
it can absorb energy and pass into the
opposed orientation. It can also lose this
extra energy and relax back into aligned
position.
• The energy of a nucleus in the presence of a
externally applied magnetic field is given by:

14. • E=-mI μ BoB
I
μ=magnetic moment of the nucleus.
B = Value of a single nuclear magneton
Bo= Magnetic flux density of the external magnetic
field

15. • The precessing proton will absorb energy
only if from radiofrequency source only if
the precessional frequency is same as the
frequency of r.f. beam.
• Hence when proton is exposed to
external magnetic field the protons will
precess , they may not all precess at the
same frequency these precessing protons
will absorb radio frequency energy of the
appropriate frequency and promote
proton from lower energy state to higher
energy state, this energy absorption is
recorded in the form of NMR spectra.

16. • The only nucleus that exhibit NMR phenomenon
are those for which spin quantum no (I) is
greater than 0…
• I is associated with mass no and atomic no.
• Mass no Atomic no I….
odd Odd/even ½,3/2,5/2
e.g.1H1.17O8
even even 0
e.g.12O6,34S16
even odd 1,2,3,..
E.g.1H2,7N14
• All nuclei having I=0 are non magnetic
• Other imp magnetic nuclei that have been
studied are 11B,14N,17O,19F,31P.

17. • The frequency at which absorption occur
can be used for qualitative analysis .
• The decrease in intensity of incident
radiation owing to absorption during a
particular transition is related to no of
nuclei in the sample that undergo
transition which can be use for
quantitative analysis.

18. • Relaxation processes
• When a nuclei is expose to r.f. radiation of
suitable frequency absorption occurs because
of the slight excess of lower energy state nuclei
present in strong magnetic field.
• Hence to obtain a readily detectable absorption
signal relaxation should occur as rapidly as
possible. i.e. lifetime of excited state should be
less.
• However disadvantage is that inverse
relationship between lifetime of excited state
relationship and width of the absorption line.
• Thus when relaxation rates are high line
broadening is greater which prevents high
resolution measurement.
• Half life for excited state should range between
0.1 to 10 sec.

19. • There are three major relaxation
processes;
• Spin - lattice (longitudinal) relaxation
• Spin - spin (transverse) relaxation
• Quadrupolar relaxation

20. • Spin - lattice relaxation
• Nuclei in an NMR experiment are in a sample.
The sample in which the nuclei are held is
called the lattice. Nuclei in the lattice are in
vibrational and rotational motion, which creates
a complex magnetic field. The magnetic field
caused by motion of nuclei within the lattice is
called the lattice field.
• This lattice field has many components. Some
of these components will be equal in frequency
and phase to the Larmor frequency of the
nuclei of interest.
• These components of the lattice field can
interact with nuclei in the higher energy state,
and cause them to lose energy (returning to
the lower state). The energy that a nucleus
loses increases the amount of vibration and
rotation within the lattice (resulting in a tiny
rise in the temperature of the sample).

21. • The relaxation time, T1 (the average
lifetime of nuclei in the higher energy
state) is dependant on the magnetogyric
ratio of the nucleus and the mobility of
the lattice. As mobility increases, the
vibrational and rotational frequencies
increase, making it more likely for a
component of the lattice field to be able
to interact with excited nuclei.
• However, at extremely high mobilities,
the probability of a component of the
lattice field being able to interact with
excited nuclei decreases .

22. • T1 is strongly affected by mobility of
the lattice .
• T1 increases as the mobility decreases.
• As the mobility increases e.g. at a high
temperature vibrational and rotational
frequencies increases which increase
the probability of magnetic
fluctuations.
• In gases and low viscosity liquids T1 is
short while in high viscosity liquids and
solids T1 is long (0.001-100sec)
• T1 should range between 0.3 – 3 sec.

23. • At equilibrium in a magnetic field the
relative number of nuclei in each of the
energetic levels in the absence of an
applied radiofrequency field can be
calculated by using this boltzman
equation.

24. • Boltzman equation to calculate radio
frequency field….
nH = e- μ BoB/IkT
nL
μ=magnetic moment of the nucleus.
B = Value of a single nuclear magneton
Bo= Magnetic flux density of the external magnetic
field
I=spin quantum no.
nL=no of nuclei in lower energy levels
nH=no of nuclei in higher energy levels
K=boltzman constant

25. • Spin - spin relaxation
• Spin - spin relaxation describes the interaction
between neighbouring nuclei with identical
precessional frequencies but differing magnetic
quantum states.
• In this situation, the nuclei can exchange
quantum states; a nucleus in the lower energy
level will be excited, while the excited nucleus
relaxes to the lower energy state.
• There is no net change in the populations of
the energy states, but the average lifetime of a
nucleus in the excited state will decrease. This
can result in line-broadening

26. Quadrupolar Relaxation
• Occurs when quadruppolar nuclei are
surrounded by asymmetrical electron clouds.
• Nuclei that have I>1/2 have spherical charge
distribution if electron distribution is
asymmetrical the electrical field fluctuates
which exert a force on quadrupolar nucleus that
changes the orientation of the nucleus in the
mag field.
• Hence interaction between nucleus and
electrical field can only occur if both have
asymmetrical charge distribution.
• If quadrupolar relaxation time is long
neighboring nucleus experience magnetic
moments of both upper and lower energetic
levels and spectral peak is split i.e. call spin
spin spliting.

27. • Chemical shift
The chemical shift is reported as a relative
measure from some reference resonance
frequency.
• An NMR spectrum is a plot of the radio
frequency applied against intensity of the
peak.
• The frequency of a signal is known as its
chemical shift.
• The chemical shift in absolute terms is defined
by the frequency of the resonance expressed
with reference to a standard compound which
is defined to be at 0 ppm. The scale is made
more manageable by expressing it in parts per
million (ppm) and is indepedent of the
spectrometer frequency.

28. • The chemical shift is caused by small magnetic
field that are generated by electrons as they
circulate around the nuclei.
• These fields oppose the applied external field .
• As a result the nuclei will are exposed to an
effective field that is somewhat smaller than
the external field.
• Bo=Bappl – б B appl
• =Bappl(1- б)
• Bappl is the applied magnetic field Bo is
resultant field which determine resonance
behaviour of the nucleus.
• Б is screening constant which is determine by
electron density and its spatial distribution
around the nucleus.

29. • This difference between the frequency of
the signal and the frequency of the
reference is divided by frequency of the
reference signal to give the chemical shift
• The frequency shifts are extremely small
in comparison to the fundamental NMR
frequency and so are generally expressed
as parts per million (ppm)..

30. It is often convienient to describe the relative positions
of the resonances in an NMR spectrum. For example, a
peak at a chemical shift, d, of 10 ppm is said to be
downfield or deshielded with respect to a peak at 5
ppm, or if you prefer, the peak at 5 ppm is upfield or
shielded with respect to the peak at 10 ppm.

31. Typically for a field strength of 4.7T the resonance
frequency of a proton will occur around 200MHz and for
a carbon, around 50.4MHz. The reference compound
is the same for both, tetramethysilane (Si(CH3)4 often
just refered to as TMS).

32. • Advantage of using TMS as internal std:
• It has 12 magnetically equivalent protons and
gives intense sharp peak.
• Has lower boiling point so recovery of analyte is
possible.
• Soluble in most of the solvents except water
and D20 so we use use sodium salt of TMS.
• Added in conc of 0.01 to 1 %.
• Structure of TMS:
Me
Me Si Me
Me

33. • Other reference compounds include..
• TMS:-for 13C and 1H
• CFCl3:-for 19F
• Conc. H3PO4:-31P
• Nitro methane:-15 N

34. • The various factors include:
• inductive effects by electronegative
groups
• magnetic anisotropy
• hydrogen bonding

35. • Electronegativity
• The electrons around the proton create a
magnetic field that opposes the applied
field. Since this reduces the field
experienced at the nucleus, the electrons
are said to shield the proton. It can be
useful to think of this in terms of vectors....
Electronegative
compd
Δ value
Iodine 2.16
Bromine 2.65
Chlorine 3.1
Flourine 4.26

36. •Since the field experienced by the proton
defines the energy difference between the two
spin states, the frequency and hence the
chemical shift, δ /ppm, will change depending on
the electron density around the proton.
• Electronegative groups attached to the C-H
system decrease the electron density around the
protons, and there is less shielding (i.e.
deshielding) so the chemical shift increases.
•This is reflected by the plot shown in the graph
hown above.

37. • These effects are cumulative, so the
presence of more electronegative groups
produce more deshielding and therefore,
larger chemical shifts.
• disruption of electron density has an
influence further down the
chain. However, the effect does fade
rapidly as you move away from the
electronegative group. As an example,
look at the chemical shifts for part of a
primary bromide

38. •Magnetic Anisotropy:-
• molecule shows both shielding and
deshielding effect
• Anisotropic grp is a grp of atoms, bonds,
or collection of electrons in which
orientation of grp defines the direction of
motion of electrons in grp
• E.g. like aromatic compd, aldehyde,
alkene where π electrons are involved
• BENZENE: if ring is oriented so that the
plane of ring is perpendicular to Bo
• Π e- are relatively free and move in a
direction shown below

40. • Because the magnetic field i.e. caused by
e- is circular, it opposes Bo at the interior
of the ring while reinforces the field in the
external plane of the ring
• Most of the chemical substituent on an
aromatic ring are in external plane of ring
• So magnetic field experienced by those
nuclei is greater
• V at which absorption occur increses
• Chemical shift increases

41. • If ring is parallel
• Little circulation of e- is possible due
to the oreintation Π e-
• So no enhancement or decrease in
Bo experienced by nucleus is seen

43. • Hydrogen Bonding:
• If analyte proton is present in stearically
hindered position that is near bulky group
electron cloud of analyte proton and bulky
group proton come near to each other
so repulsion of 2 clouds so analyte proton
will exp more Bo and thus deshielding
occur
increase in the δ value.

44. Spin spin coupling:spilitting of
signals
• Spilliting of signals can be determined by
environment of the absorbing proton with
respect to neighbouring protons
• Because of diff spin states & the resulting
magnetic moment of neighbouring
protons, the actual field experienced by
proton may be modified
• Thus it is the spin spin coupling of
absorbing and neighbouring proton which
is responsible for splitting

45. • Consider the structure of ethanol;
• The 1H NMR spectrum of ethanol (below)
shows the methyl peak has been split
into three peaks (a triplet) and the
methylene peak has been split into four
peaks (a quartet).
• This occurs because there is a small
interaction (coupling) between the two
groups of protons.
• The spacings between the peaks of the
methyl triplet are equal to the spacings
between the peaks of the methylene
quartet.
• This spacing is measured in Hertz and is
called the coupling constant, J.

47. • To see why the methyl peak is split into a
triplet, let's look at the methylene
protons. There are two of them, and each
can have one of two possible orientations
(aligned with or opposed against the
applied field). This gives a total of four
possible states;

50. Rules for splitting of proton signals
• Spilliting is caused only by neighbouring
or vicinal protons which are not equivalent
to proton under consideration
• Equivalent nuclei do not interact with each
other. For e.g.. the three methyl protons in
ethanol cause splitting of the
neighbouring methylene protons; they do
not cause splitting among themselves
• No of peak into which a proton signal is
split up is equal to one or more than the
no of vicinal protons)
N=n+1

51. • All the peaks of a given multiplet are
not of exactly the same intensity. It
has been observed that the inner peaks
are larger than the outer peaks

52. • Other examples:-
• CH3-CH2-CH2-NO2
• Triplet sextet triplet
H
• CH3-C-COOH CH3-doublet
CH-quartet
Cl COOH-singlet
2,chloro propanoic acid

53. Coupling constants:-
• The distance between the peaks in a
given multiplet is referred to as
coupling constant
• Is denoted by J
• Expressed in Hz or cps
• unlike the chemical shift the values
of J are independent of applied field
strength and dependant only upon
the molecular stru.

54. Factors influencing the
coupling constant
• J can have positive or negative values
• The no of bonds intervening between the
coupling nuclei is imp since coupling is
transmitted via the electrons of these
bonds
• It is a convenient notation that indicate
this no as a superscript to the symbol for
coupling constant
• Direct coupling would be one bond
coupling,1J

55. Types of coupling:-
• Geminal coupling:-
 coupling of CH2 grp
 2J=10-18 Hz
• vicinal coupling:-
 coupling of H with H of adjacent carbon atom
 3J=0-12Hz;if molecule is rigid
 3J=8Hz; if molecule is flexible
• long range coupling:-
 observed in alkanes
 lesser J value

56. • Trans coupling:-
observed in alkenes
 J=11-19Hz for trans comp.
 J=5-14 Hz for cis compds
• Aromatic coupling:-
 if ortho H is involved: J=7-10Hz
 if meta H is involved: J=2-3 Hz
 if pera H is involved: J=0-1 Hz
• Allylic coupling:-
observed in non aromatic comp. wh9ich
are allylic in nature
 J=0-2 Hz

58. Chemical and magnetic
equivalence
• Two protons are chemically equivalent if
their electronic environment are same
because of symmetry of molecule and therefore
they possess same δ value
• Two protons are magnetically equivalent if
each proton couples equally to a third
neighboring proton
• So if 2 protons are chemically nonequivalent
must be magnetically nonequivalent
• And if they are chemically equivalent maybe
magnetically equivalent

59. Types of NMR spectra
• low resolution/ high resolution
• wide line spectra
• lower Bo -higher Bo
• characteristic band -more than 1
appear peak appear
• used only for -for quantitative/
quantitative analysis and qualitative
analysis
• recorded for isotopes for functional grps

60. Instrumentation:-
• Types of NMR high resolution spectra
Continuous wave Fourier trnsform
NMR NMR
• Imp parts of the NMR spectrometer:-
 Permanent magnet/electromagnet
 Rf generator
 Rf detector
 Sample holder
 Magnetic coils

61. • Principle:- based on
• frequency sweep field sweep
fre. Of rf source fre is constant
is varied
Bo is constant Bo is varied

62. CONSTRUCTION:-
• Magnets:-
• permanent:- constant Bo is generated that is
0.7;1.4;2.1
• adv:-
• construction is simple
• cheaper
• electromagnet:-Bo can be varied which is
done by winding the electromagnetic coil
around the magnet
• most expensive components of the nuclear
magnetic resonance spectrometer system

63. • Shim Coils
• The purpose of shim coils on a
spectrometer is to correct minor spatial
inhomogeneities in the Bo magnetic field.
• These inhomogeneities could be caused
by the magnet design, materials in the
probe, variations in the thickness of the
sample tube, sample permeability.
• A shim coil is designed to create a small
magnetic field which will oppose and
cancel out an inhomogeneity in the Bo
magnetic field.

64. •Superconducting solenoids:-
• prepared from superconducting
niobium-titanium wire and niobium-
tin wire
• operated at lower temp.
• kept in liq He(mostly preferred) or
liq N2 at temp of 4 K
• liq N2 shd be changed at 10 days
while liq He shd be changed at 80-
130 days
• higher Bo can be produced that is
upto 21 T

65. •Advantage:-
High stability
Low operating cost
High sensitivity
Small size compared to electromagnets
simple

66. RADIOFREQUNCY TRANSMITTER
• It is a 60 MHz crystal controlled oscillator
• Rf signal is fed into a pair of coils mounted at
right angles to the path of field
• The coil that transmit rf field is made into 2
halves in order to allow insertion of sample
holder
• 2 halves are placed in magnetic gap
• For high resolution the transmitted fre must be
highly constant
• The basic oscillator is crystal controlled
followed by a buffer doubler, the fre being
doubled by tunning the variable

67. • It is further connected to another
buffer doubler tuned to 60 MHz
• Then buffer amplifier is provided to
avoid circuit loading

68. Signal amplifier and
detector
• Radiofrequency signal is produced by the
resonating nuclei is detected by means of
a coil that surrounds the sample holder
• The signal results from the absorption of
energy from the receiver coil, when
nuclear transitions are induced and the
voltage across receiver coil drops
• This voltage change is very small and it
must be amplified before it can be
displayed

69. The display system
• The detected signal is applied to
vertical plates of an oscilloscope to
produce NMR spectrum
• Spectrum can also be recorded on a
chart recorder

70. • Sample Probe
• The sample probe is the name given to that
part of the spectrometer which accepts the
sample, sends RF energy into the sample, and
detects the signal emanating from the sample.
• It contains the RF coil, sample spinner,
temperature controlling circuitry, and gradient
coils.
• It is also provided with an air driven turbine for
rotating the sample tube at several hundred
rpm
• This rotation averages out the effects of
inhomogeneities in the field and provide better
resolution

71. Continuous wave NMR
• It consist of control console, magnet,
and 2 orthogonal coils of wire that
serves as antennas for rf radiation
• One coil is attached to rf generator
and serves as transmitter
• The other coil is the rf pick up coil
and is attached to detection
electronics

73. • Since the 2 coils are orthogonal, the pick
up coil cannot directly receive any
radiation from generator coil
• When a nucleus absorb rf radiation, it can
become re oriented due to i9ts normal
movement in sol and re emit the rf
radiation in a direction that can be
received by the pick up coil
• Spectra are obtained by scanning the
magnet and recording the pick up signal
• CWNMR are largely replaced by pulsed
FTNMR
• However due to lower operating and
maintaining cost, they are still used

74. •Pulsed Fourier Transform
Spectroscopy

76. • FTNMR uses a pulse of rf radiation which
causes a nuclei in a magnetic field to flip into
higher energy alignment
• Applying such a pulse to a set of nuclear spins
simultaneously excites all the nuclei in all local
environment.
• All the nuclei will re emit rf radiation at their
resonance frequencies which induces a current
in a nearby pickup coil, creating an electrical
signal oscillating at the NMR frequency. This
signal is known as the free induction decay
(FID) and contains the sum of the NMR
responses from all the excited spins.

77. • In order to obtain the frequency-domain NMR
spectrum (intensity vs. frequency) this time-
domain signal (intensity vs. time) must be
Fourier transformed. Fortunately the
development of FT-NMR coincided with the
development of digital computers and Fast
Fourier Transform algorithms.

78. • . This is the principle on which a pulse
Fourier transform spectrometer operates.
By exposing the sample to a very short
(10 to 100 μsec), relatively strong (about
10,000 times that used for a CW
spectrometer) burst of rf energy, all of
the protons in the sample are excited
simultaneously.
• In a given strong external magnetic field,
each structurally distinct set of hydrogens
in a molecule has a characteristic
resonance frequency,

79. • Advantage over continuous wave
NMR
 Sample of low conc. can be determined
 Magnetic nuclei with low natural isotopic
abundance can be determined eg 13C
 Very rapid pulse repetition can be possible
 Entire spectrum can be recorded, computerized
and transformed in a fewb seconds that is
every 2 sec
 For e.g. in 13 min 400 spectra can be recorded
 So thus 20 times signal enhancement is seen
 Analysis can be possible where magnetogyric
ratio is low

80. Solvents used in NMR
• Properties:-
Nonviscous
Shd dissolve analyte
Shd not absorb within spectral range
of analysis
All solvents used in NMR must be
aprotic that is they shd not possess
proton

81. • Chloroform-d (CDCl3) is the most
common solvent for nmr measurements
• other deuterium labeled compounds,
such as deuterium oxide (D2O),
benzene-d6 (C6D6), acetone-d6
(CD3COCD3) and DMSO-d6
(CD3SOCD3) are also available for use
as nmr solvents.
• DMF, DMSO, cyclopropane, dimethyl
ether can also be used

82. Applications:-
• Qualitative:-
 Structural elucidation of organic compd,
bochemical molecules
 No of signals:- gives idea about no of type pf
proton present
 Position of signal:- gives idea about
electronic environment of each proton
 Intensity of signal:- gives idea about how
many no of proton are present in each
environment
 Splitting of signal:- indicate neighbouring
proton with respect to analyte proton

83.  The chemical shift of each environmentally
diff nucleus is measured and used in
conjunction with correlation such as
group Δ value
(CH3)4Si 0
ROH 0.5
RNH2
CH3CX
0.5-2
1.0-2.0

84. The integrations of spectral peaks are
used to determine the relative no of
nuclei in the sample that are associated
with each grp
The splitting patterns of peaks peaks are
used to determine the no of magnetic
nuclei in the vicinity of nucleus.
The integrated areas are used in
conjunction with splitting patterns to
determine groups that are adjacent to
each other

85. Shift reagents:-
• Mainly used when spectra that contain:
 Overlapping peaks can be difficult to
interpret
 Spilliting patterns are difficult to detect
and interpret
 Peak area that can’t be obtained
• So shift reagents can be used to
separate the peaks
• It consist of organometallic complex of
one of LANTHENIDE salts

86. • Metal exert electrostatic force through
space on magnetic nuclei of sample
• This force causes a change in extent of e-
shielding around the nucleus
• This causes a change in chemical shift
• This δ is large and can be as much as 20
ppm
• Only nuclei near bonding site with the
shift reagent are affected

87. • LANTHENIDE element include:-
• Europium; holmium; ytterbium;
praseodymium
• Europium causes downfield shift while
praseodymium causes upfield shift
• Upfield shift can’t be accounted for by the
mech described above

88. •Quantitative:-
• NMR spectra is direct proportionality between
peak area and no. of nuclei responsible for
peak
• Measurement is done by caliberation curve and
internal std
• it involves estimation of following:
 Multicomponent mixture:-
 Determination of benzene, haptane, ethylene
glycol, water in mixtures
 Of functional groups present in molecules
 E.g. OH in alcohol, olefines in acetylinic
hydrogens, amides

89. • Elemental analysis:-
• Used to determine total conc. of given
NMR active nucleus in sample
• Determination of total H in a given
mixture
• Determination of minor components
like impurities, excipients