- Science Honors Program -
Computer Modeling and Visualization in Chemistry
The Basics of NMR
Nuclear magnetic resonance
Spectroscopy is the study of the interaction of
electromagnetic radiation with matter.
NMR spectroscopy has only been important in
organic chemistry since the mid-1950s.
The versatility of NMR makes it pervasive in the
various fields of science.
Basis of NMR
When exposed to a magnetic field, magnetic
nuclei can receive & emit radio waves
The frequency, 0 , is proportional to the
strength, B0 , of the magnetic field:
0 = 2 0 = B0
is the gyro-magnetic ration. It is a
characteristic constant of the nuclear isotope.
Nuclei Unpaired Protons Unpaired Neutrons Net Spin (MHz/T)
1H 1 0 1/2 42.58
2H 1 1 1 6.54
31P 0 1 1/2 17.25
23Na 2 1 3/2 11.27
14N 1 1 1 3.08
13C 0 1 1/2 10.71
19F 0 1 1/2 40.08
Nuclear Spin: Classical View
Nuclear Magnetization in Thermodynamic Equilibrium
d = (n - nREF) x106 / nREF
Fourier Transform (FT)-I
An FT is defined by the integral
Think of f( ) as the overlap of f(t) with a wave of frequency .
This is easy to picture by looking at the real part of f( ) only.
Consider the function of time, f( t ) = cos( 4t ) + cos( 9t )
Interaction J (Hz)
NMR Lock Solvents
Dichloro Methane CD2Cl2
Diethylether (DEE) (CD3CD2)2O
Dimethylether (DME) (CD3)2O
N,N-Dimethylformamide (DMF) (CD3)2NCDO
Dimethyl Sulfoxide (DMSO) CD3SOCD3
Tetrehydrofuran (THF) C4D8O
Some examples (1H NMR)
Integration and # of scan
2-D techniques (COSY)
Advanced spectroscopic techniques
The motion involved in NMR spectroscopy is that
of nuclear spin.