Figure 9.36
(a) 60 MHz proton NMR spectrum of n-hexanol.
(b) 100 MHz proton NMR spectrum of n-hexanol with 0.29 mole equivalents of
Eu (dpm) 3 added.Carbon-13 NMR
Carbon-13 spectra are inherently less complex than proton spectra for two reasons, viz.: (a) chemical
shifts between^13 C nuclei in different chemical environments can differ by as much as 200 ppm whereas
proton shift differences are seldom more than 10 ppm: (b) as the natural isotopic abundance of^13 C is
only 1.1%, coupling between^13 C nuclei themselves is not observed (but see 2-D INADEQUATE
spectrum, p. 420).
Coupling between^13 C nuclei and protons, however, does occur but in practice this can be eliminated by
noise decoupling which leads to even simpler spectra. Noise decoupling consists of irradiating the
sample over a wide frequency range covering all the proton resonances in the sample (white noise
irradiation) whilst observing the^13 C signals. In some cases^13 C-proton coupling can provide useful
structural information and this can be