Transcript CH 9-7 Power Point

CH 9-7: Topic 5 - 13C NMR
•13C NMR gives direct information about the number of
non-equivalent carbons. ONE signal per equivalent carbon.
•13C NMR chemical shift scale ranges from 0 - 220 ppm, so
signals from similar carbons are less likely to overlap.
•Only the spinning nuclei of the 13C isotope gives an NMR
signal (not 12C). Only 1% of all carbon in nature is the 13C
isotope. 6400 times less sensitive than 1H NMR.
•Since only 1% of all C is 13C, no splitting is seen by
adjacent carbons - very small probability that there will be
two 13C carbons next to each other! Easier to interpret.
•It is possible to observe H-C splitting which is very useful:
(a) “Proton Decoupled” 13C NMR (no C-H splitting)
(b) “Proton Coupled” 13C NMR (shows C-H splitting)
2-butanol “Proton Decoupled” 13C NMR
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2-Butanol “Proton Coupled” 13C NMR
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(solvent)