2D NMR Experiments gCOSY (gradient COrrelation SpectroscopY ...

2D NMR Experiments
gCOSY (gradient COrrelation SpectroscopY): a two‐dimensional NMR
technique where the cross‐peaks appear between protons that have 3‐
bond proton‐proton scalar coupling, 3 J HH
ROESY (Rotating‐frame Overhauser Effect SpectroscopY): a twodimensional
NMR technique where the cross‐peaks appear between
protons that are within 6 Å of each other, the closer in space the two
protons are to each other the more intense the cross‐peak
NOESY (Nuclear Overhauser Effect SpectropY): a two‐dimensional NMR
technique where the cross‐peaks appear between protons that are within 6
Å of each other, the closer in space the two protons are to each other the
more intense the cross‐peak
gHSQC (gradient Heteronuclear Single Quantum Coherence): a two
gHSQC (gradient Heteronuclear Single Quantum Coherence): a twodimensional
NMR technique where one axis is 1 H and the other is 13 C. This
experiment does not have a diagonal and peaks appear for one‐bond H,Ccorrelation.

Optimizing your setup
Step 1 Tune the NMR to your sample gives you the best sensitivity/resolution for 2D
use mtune to adjust to get best dip
Step 2 Lock and shim gives you best resolution/lineshape
If you want to ensure that the instrument is in a good state when you begin do 3
things, load in fresh parameters for your experiment and load in fresh shims then type su.
Step 3 Determine the 1 H and 13 C pw 90 for your sample give best sensitivity with least
amount of artifacts for 2D experiments
a. 1 H pw 90
not that important for gCOSY
b. only need to do 1 H pw for ROESY and NOESY but you need to determine the
1 90
H pw 90
and the 13 C pw 90
for gHSQC
How to determine pw 90
for your sample
array the parameter pw and look for the 360⁰ null and then divide that
number by 4
Procedure:
load in 1D 1 H proton experiment
tune and shim your sample
type d1=10
type pw90 to get default pw 90
value
array parameter pw to 4*pw 90
±10 (type (yp array follow instructions)
repeat array command with 0.2 µsec step size around best 4*pw 90
value determined above

Determining the optimum mix time for your sample
Run a 1D NMR of your sample
Load the selective 1D experiment that you plan to do a 2D version of later
Select an area of the spectrum to excite by putting cursors around it and clicking first
select then proceed
Array the mix time for 0.2 to 1
Find the NOE/ROE peak that has the highest intensity and use it’s mixing time in your 2D
experiment
What am I observing
Lets say you select an aromatic peak in your 1D 1 H spectrum to selectively
excite then you run the Noesy1d. The spectrometer will acquire a 1D 1 H spectrum and
only excite the peak you selected, any other peaks that appear in the spectrum are NOE
peaks whose intensity depends on the mixing time.

Setting up the 2D experiment
1) In setting up a 2D experiment you either add a proton experiment or one will be added
for you before your 2D experiment.
In the proton experiment either set the spectral width to the desired range or
turn off minsw
Type pw90=your empirically determined pw 90
for your sample
then type pw=pw90
2) For all NMR experiments the number of scans is a function of concentration, ti less
concentrated means you need to do more scans
Signal‐to‐noise is proportional to (number of scans) 2
‐so if you half the concentration you need to do four times the number
of scans
*In general it is better to increase the number of scans over the number of
increments

Experiment specifics
gCOSY
What to change
two parameters
1. number of scans that you do per increment improves signal‐to‐noise
2. number of increments improves resolution
both of these will increase experimental time
generally 1 scan and 128 increments will give you acceptable spectra
NOESY
What to change
three parameters
1. number of scans that you do per increment improves signal‐to‐noise
noise
2. number of increments improves resolution
3. mixing time this is a parameter that affects the intensity of the crosspeak you
observe, too short of the time and the crosspeak intensity will not have time to develop, too
long of a time and the signal will relax back to equilibrium i and you’ll lose the crosspeak
‐either determine mix experimentally or use 800 milliseconds
8 scans and 128 increments is acceptable

ROESY
What to change
three parameters
1. number of scans that you do per increment improves signal‐to‐noise
noise
2. number of increments improves resolution
3. mixing time this is a parameter that affects the intensity of the crosspeak you
observe, too short of the time and the crosspeak intensity will not have time to develop, too
long of a time and the signal will relax back to equilibrium and you’ll lose the crosspeak
‐either determine mix experimentally or use 800 milliseconds
8 scans and 128 increments is acceptable
gHSQC
What to change
five parameters
1. number of scans that you do per increment improves signal‐to‐noise
2. number of increments improves resolution
3. how you want to handle multiplicity (yes or no)
4. spectral range of the 13 C axis
5. 1 J CH
one‐bond carbon‐proton coupling constant, default is 140 Hz
2 scans and 128 increments is acceptable