Carbon-13 NMR satellite

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In an NMR spectrum the presence of 1% of the NMR active 13C species 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).

[edit] Uses

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 stilbene Ph-=-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.

[edit] See also

not to be confused with side band spinning effect,
1H NMR
13C NMR

[edit] References

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 [1]
Y. Ogimura, S. Fujiwara and K. Nagashima, Chemical Instrumentation 1, 21 (1968); S. Fujiwara, Y. Yano and K. Nagishima, Chemical Instrumentation 2, 103 (1969); S. Fujiwara, Magnetic Resonance, ed., C. K. Coogan et a!., Plenum Press, New York (1970).
H. Ozawa, Y. Arata and S. Fujiwara, J. Chem. Phys., to be published.
S. Forsén and R. A. Hoffman, J. Chem. Phys. 40, 1189 (1964); R. A. Hoffman and S. Forsén, J. Chem. Phys. 45, 2049 (1966).
N. Bloembergen and R. V. Pound, Phys. Rev. 95, 8 (1954); S. Bloom, J. App!. Phys. 28, 800 (1957).
A. O. Niel, Phys. Rev. 77, 789 (1950).
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