- Carbon-13 NMR satellite
NMR spectrumthe presence of 1% of the NMR active carbon-13species will cause coupling. This will split 1% of the peak into a doublet. These are called satellites as they small and are around the main non-coupled peak like little shoulder peaks.
This is usually seen in the 1H-NMR, as small shoulder peaks, but can be seen in 19F or 31P NMR, as long as these atoms are on a carbon atom that is the spectrum is not 13C-decoupled (usually the case).
Can be used to obtain structural information, due to de-symmetry as compared to 99% of molecule where C atom is 12-C.
For example, you can not tell if
stilbenePh-=-Ph is cis- or trans- bonded just by looking at the 1H NMR of the protons on the double bond, without reference to any other material, as they do not couple (molecule is symmetric). However 1% of molecules will have a 13C atom on one of these double bond carbons. The protons on these atoms will be 13C coupled and give a doublet. However, this molecule is not symmetric and the protons on the double bond couple. The coupling in the satellite peaks (i.e. a double of doublets i.e. one 13C coupling and one cis-/trans- 1H coupling) in the double bond of Ph-=-Ph will tell you if it is cis- or trans- bonded by the size of the J splitting in the 1H constant.
* not to be confused with side band spinning effect,
* NMR SATELLITES AS A PROBE FOR CHEMICAL INVESTIGATIONS SHIzuo FUJIWARA, Yogi ARATA, HIR0sHI OZAWA and MASAYUKI KuruGI Department of Chemistry, The University of Tokyo, Japan [http://old.iupac.org/publications/pac/1972/pdf/3201x0117.pdf]
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* Geometry determination of tetrasubstituted stilbenes by proton NMR spectroscopy, Viviana S. Fluxáa, Titus A. Jennya and Christian G. Bochet, Tetrahedron Letters, Volume 46, Issue 22, 30 May 2005, Pages 3793-3795
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