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NMR Spectroscopy

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					          NMR Spectroscopy

             Two-dimensional NMR



http://www.univ-lille1.fr/lcom/RMN2D/resum2D_us/index_us.htm
                 1D NMR

Pulse Sequence




Spectrum
(EtOH)
 Four periods in 2D experiment



Preparation     spin system relaxes and then excited by r.f.
Evolution (t1) chemical shifts & spin-spin couplings evolve.
               This is the timedomain which is incremented
               during a 2D experiment
Mixing          r.f. pulses are applied and create observable
                transverse magnetization
Detection (t2) observable transverse magnetization is recorded. It is
               usually labeled with t2
                      2D NMR
1. Primary 2D matrix consists a series of FIDs.
2. A set of 1D NMR spectra is obtained by Fourier transformation
   with respect to t2
3. The signals of each transformation may differ in amplitude and
   phase. A second Fourier transformation with respect to t1 yields
   the final 2D matrix with frequency axes F1 and F2




       1.                     2.                    3.
                    2D NMR

Pulse Sequence




         Spectrum
2D NMR
2D NMR
2D NMR
   2D J-resolved


   COSY 45. COSY 90.
   COSY DQF. TOCSY.




  COSY L.R. TOCSY




Relayed COSY. (with one
     homonuclear
       relayed).




  NOESY.      ROESY.
2D J-resolved spectroscopy
H,H- COSY Experiment
COSY & TOCSY
TOCSY of strychnine
NOESY of strychnine
C,H Correlation by Polarization Transfer
              (HETCOR)
HMQC
The HMQC experiment provides correlation between protons
and their attached heteronuclei through the heteronuclear
scalar coupling.
HMBC
The HMBC experiment suppresses correlations via 1JC,H while
2J, 3J can be conserved.



HSQC
The HSQC experiment is in fact a double INEPT experiment.
This experiment correlates protons with their directly
attached heteronuclei.
(G. Bodenhausen and D. J. Ruben, Chem. Phys. Lett., 69, 185 (1980)
Basic HMQC Experiment

F2 displays the doublets
with the spin coupling
constant 1J(C-H) in
addition to the H,H spin
coupling.
 HMQC with Decoupling


Only singlets are displayed
in F2 . These signals are
further split by H,H spin
couplings.
Basic HMBC Experiment

Cross signals caused
by 1J of C-6 and C-3
are still observable
but those arising
from 3J and 2J are
predominant.
Basic HSQC Experiment
COSY
DQF-COSY
HMQC
HMBC
HSQC

				
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posted:10/16/2012
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