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Introduction
 NMR srectroscopy is the study of spin changes at the nuclear
level when radio frequency energy is absorbed in the presence of
magnetic field.
 Nuclei with odd mass number only Nuclei with odd mass number
only give NMR spectra.
eg:1H,13C,19F,35Cl
 NMR Spectroscopy is an important method for molecular
structural determination

This spectroscopy gives information about the number
and types of protons in a molecule.
Different types of NMR spectroscopy are available
1H-NMR
spectroscopy
13C-NMR
spectroscopy
31P-NMR
spectroscopy
29Si-NMR
spectroscopy
Fourier-transform NMR
Solid state NMR
19F, 119Sn, 195Pt, 123Te,129Xe
etc.
PRINCIPLE:
 Any nucleus with odd mass number spins on its own axis.
 By the application of an external magnetic field the nucleus
spins on its own axis and magnetic moment created.This
state is called ground state.
 The magnetic field caused by the spin of nuclei aligned with
externally applied magnetic field.When energy applied in
the form radiofrequency,absorption of energy occur and
NMR signal is recorded.
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INSTRUMENTATION
 Magnet poles
 Sample cell(tube )
 Sweep generator
 RF transmitter
 RF receiver
 Recorder
INSTRUMENTATION
 Magnet poles:
 Generation of magnetic field.
 Sweep generator:
 To vary the strength of applied magnetic field.
Eg:14,092 gauss,21,140gauss.
• RF receiver:
To Measure the intensity of unabsorbed radio frequency
energy.
 RF transmitter:
Used to apply radiofrequency radiation.
Eg:60MHz,90MHz,100MHz,220MHz.
 Sample cell:
sample test tube which is about 25mm long and 5mm
diameter.
This is kept inside the sample cavity and is spun at 30rps.
Recorder:

Record NMR signal obtained from detector.
Parameters
involved in NMR
 Relaxation process
 Shielding and desheilding
 Chemical shift
 Spin-Spin coupling
 Relaxation process:
It is the process of transmission from excited state to
ground state. Where the absorbed enegy can be lost by Two ways
Spin-lattice(longitudinal)
Spin-Spin(Transverse)
Spin-Spin(Transverse):
It involves the transfer of energy from one
nucleus to the other. There is net loss of energy.
Spin-lattice(longitudinal):
• It involves the transfer of energy from the nucleus in
its higher energy state to the molecular lattice.
•
The energy is transferred to the components of the
lattice as the additional transitional, vibrational and
rotational energy.
•
Thus the total energy of the system remains the same.
Shielding and desheilding:
Nucleus is surrounded by the electrons.Protons can be
present within or outside the magnetic field caused by the
electrons in double bond.
 When a proton is present inside magnetic field more applied
magnetic field is required to cause excitation.such protons are
called Shielded protons.
 When a proton is present outside the magnetic field less applied
magnetic field is required to cause excitation.such protons are
called deShielded protons.

SHEILDING AND DESHIELDING
 Chemical shift:
chemical shift is the difference between the
absorption position of a sample and the absorption
position of the reference compound.TMS (tetra
methyl silane) used as reference compound.
Tetra methyl silane (TMS)
 For a 1H-NMR spectrum, signals are reported by their shift
from the 12-H signal in TMS.

For a 13C-NMR spectrum, signals are reported by their shift
from the 4-C signal in TMS.

Chemical shift (δ): the shift of an NMR signal from the signal of
TMS. Normally given in parts per million (ppm).

TMS is not useful for water soluble compounds,for this DSS
used.(DSS-2,2-dimethyl-2 silapentane-5-sulphonate)
Spin - spin coupling:
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 effect of the methyl protons on the methylene protons will
be present.
 .The splitting pattern of a given nucleus can be predicted by the
n+1 rule, where n is the number of neighboring spin-coupled
nuclei.
 Coupling constant:
The distance between the two peaks. It is
represented by J
Spin-Spin coupling/splitting
INTENSITY RATIO
Solvent requirements
 Solvent used in NMR soectroscopy should not contain
Hydrogen atoms.
 Hence we use solvents like carbon tetra
chloride(ccl4),deuteratedachloroform(CDCl3),Deutera
ted water, Deuterated dimethyl sulphoxide.
Properties of solvent
 Chemical inertness
 Magnetic isotropy
 Volatility
 Absence of hydrogen atoms
 Easily available
 Inexpensive
Applications
 Structure elucidation of organic compounds.
Types of protons
Environment of protons
No.of protons of each type
No.of adjacent protons
 Investigation of
conformational isomerism,
molecular symmetry
hydrogen bonding
keto-enol tautomerism
 Determination of optical purity.
 Study of molecular interaction
micelle formation
Drug receptor interaction
 Quantitative analysis
Assay of components
Surfactant chain length determination
Hydrogen analysis
Iodine value
Moisture analysis
 Used to determine the molar ratio of the components
in a mixure.
 Analysis of mixure of isomeric compounds like oxylene and p-xylene.
 Elimental analysis.
 Rates of reaction.
limitations
 The minimum sample size is 0.1ml of 1%con
 Lack of sensitivity.
 It does n’t give information about molecular weight.
 Only liquids can be studied.
REFERENCES
•Spin Dynamics: Basics of Nuclear Magnetic
Resonance, 2nd Edition, Wiley 2008.
•Fundamentals of Nuclear Magnetic Resonance
Spectroscopy, Durham Eagle Press, Durham, North
Carolina, 2007.
Thank you