In previous posts on this BLOG, examples of 1H/2H and 12C/13C isotope effects were discussed. The figure below shows an example of a 10B/11B isotope effect observed in the 19F NMR spectrum of tetrabutyl ammonium tetrafluorobarate.
The spectrum clearly shows two resonances separated by 0.05 ppm with an intensity ratio of approximately 20:80 corresponding to the natural abundances of 10B and 11B, respectively. The low frequency resonance is due to 11BF4-. Since 11B is a spin I = 3/2 nuclide we observe a 1:1:1:1 quartet with J = 1.25 Hz corresponding to the one bond 19F - 11B coupling. The high frequency resonance is due to 10BF4-. Since 10B is a spin I = 3 nuclide we observe a very poorly resolved 1:1:1:1:1:1:1 septet with J ~ 0.4 Hz corresponding to the one bond 19F - 10B coupling.
Mechanism of Flavoprotein l-6-HydroxynicotineOxidase: pH and Solvent Isotope Effects and Identification of KeyActive Site Residues
Mechanism of Flavoprotein l-6-HydroxynicotineOxidase: pH and Solvent Isotope Effects and Identification of KeyActive Site Residues
http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/bichaw/0/bichaw.ahead-of-print/acs.biochem.6b01160/20170126/images/medium/bi-2016-01160d_0007.gif
Biochemistry
DOI: 10.1021/acs.biochem.6b01160
http://feeds.feedburner.com/~ff/acs/bichaw?d=yIl2AUoC8zA
http://feeds.feedburner.com/~r/acs/bichaw/~4/N2z8-BteVuA
More...
nmrlearner
Journal club
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01-27-2017 12:00 AM
Solvent and H/D Isotope Effects on the Proton TransferPathways in Heteroconjugated Hydrogen-Bonded Phenol-Carboxylic AcidAnions Observed by Combined UV–vis and NMR Spectroscopy
Solvent and H/D Isotope Effects on the Proton TransferPathways in Heteroconjugated Hydrogen-Bonded Phenol-Carboxylic AcidAnions Observed by Combined UV–vis and NMR Spectroscopy
Benjamin Koeppe, Jing Guo, Peter M. Tolstoy, Gleb S. Denisov and Hans-Heinrich Limbach
http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/0/jacsat.ahead-of-print/ja400611x/aop/images/medium/ja-2013-00611x_0015.gif
Journal of the American Chemical Society
DOI: 10.1021/ja400611x
http://feeds.feedburner.com/~ff/acs/jacsat?d=yIl2AUoC8zA...
nmrlearner
Journal club
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05-09-2013 04:04 AM
[U. of Ottawa NMR Facility Blog] Isotope Effects and the 19F - 13C HMQC Spectrum of Trifluoroacetic Acid
Isotope Effects and the 19F - 13C HMQC Spectrum of Trifluoroacetic Acid
The 19F - 13C HMQC spectrum of trifluoroacetic acid is shown in the figure below.
http://4.bp.blogspot.com/-roN1Zav9lO8/UIWplTlt8WI/AAAAAAAAA-o/G0N2j7vkqns/s400/tfa1.jpg
The data were collected with a delay appropriate for a 19F - 13C J coupling constant between the 1JF-C coupling constant of 284 Hz and the 2JF-C coupling constant of 44 Hz. The top and side traces are the one-pulse 19F and 13C spectra, respectively. Why are the HMQC responses not at the same 19F chemical shift and why aren't they correlated...
nmrlearner
News from NMR blogs
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10-22-2012 09:07 PM
[Question from NMRWiki Q&A forum] Help for Boron 11 NMR!
Help for Boron 11 NMR!
I'm using a Bruker 300 NMR, equipped with a BBO probe, to do Boron 11 NMR. But I got no signal no matter what pulse length or scan width I set, I don't know whether it's related with the borosilicate tubes I use, or should I use quartz ones. Could someone here give me some advice? Thank you!
Check if somebody has answered this question on NMRWiki QA forum
Boron Isotope Effects in Fluorine NMR Spectra
Linear Mode
