Department of Chemistry,
University of Alberta
NMR News 2004-02
News and tips for users of the Varian NMR systems in the Department
Editor: Albin.Otter@ualberta.ca http://nmr.chem.ualberta.ca
There are no fixed publishing dates for this newsletter; its appearance solely depends on whether there is a need to present information to the users of the spectrometers or not.
Other content of this NMR News is no longer meaningful and has been removed May 2010.
NMR data processing in the
Department Updated 2010-05-07
1) Use one of the LINUX data stations
All provide 8.5 x 11 laser printer capabilities.
2) Use a Mac or PC to remotely access a UNIX server
If you would like to add a Mac computer to this form of data processing, the following needs to be done (for PCs see below):
If you are interested in this form of data processing, please provide the following information to the editor (for the LINUX side) and the IT group (for the security part):
computer name &
computer IP (always starts with 129.128.)
Thanks to Doug Burr in Dr. Vederas' group for providing the "Mac-side" information needed to make this work.
Special note for PCs: unfortunately,
the PC/Windows world has not yet caught up to the beauty and stability of a UNIX
kernel. However, it is possible to do X-sessions with PCs as well.
a "new" spectrometer for undergraduate students
Sucrose (90 vs. 600 MHz
The 90 MHz spectrum (*) is shown on top, the 600 MHz equivalent at the bottom. Both spectra were recorded in D2O. The 600 MHz spectrum shows the quality of solvent suppression and, of course, the expected dramatic increase in signal dispersion. While the past is often referred to as the "good old days", this does certainly not apply to NMR! Other than H1g, nothing is really directly accessible for analysis at 90 MHz. Even H3f and H4f are so close at 90 MHz that they partly overlap and form a higher order spin system. Please note that only some key resonances are labeled here. A 600 MHz 2D spectrum provides, not surprisingly, a complete assignment of all protons.
|Interesting is the H1f proton pair. Even at 600 MHz the chemical shift of the
two protons is so similar that a very tight AB system is observed.
At first sight it looks like a singlet (which would entail that, through fast rotation, the two protons cannot be distinguished on the NMR time scale). However, the two small transition lines symmetrically located on both side of the intense center line clearly show that this is an AB (these are neither spinning side bands nor 13C satellites!).
Through spin simulation the chemical shift difference was found to be only 0.005 ppm (3 Hz) with a geminal coupling constant of -12.5 Hz between the two protons. It is not all that often seen at such a strong field that the coupling constant between two protons is 4 times larger than their chemical shift difference. Truly higher order!
More information on higher order effects can be found in NMR News 2003-01.
A short summary about Professor Lemieux's work is provided
here (courtesy of
Professor David R. Bundle). The same
picture as shown above but with a CPK model is also available in this
(*) We are grateful to Don White in the Department of Pharmacy for providing access to their 90 MHz FT spectrometer. It is a formidable challenge nowadays to find a field below 300 MHz and hence we are really glad we could obtain the spectrum from Pharmacy.
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