Figure 9.46
The HETCOR spectrum of geraniol, in CDCl 3 at 500 MHz for^1 H and^
125.7 for^13 C.doublets (cross-peaks) due to^13 Cā^13 C coupling, i.e. all are AX systems. The much more intense singlets
of the isolated^13 C nuclei (diagonal peaks) which are present in 99.99% of the sample are suppressed
during the pulse sequence. By making the scale of the F 1 axis, along which the 1-D^13 C spectrum is
plotted at the top, half that of the F 2 axis, the pairs of doublets separated in the F 1 direction, and which
link specific^13 C nuclei in the 1-D spectrum, appear symmetrically on either side of the diagonal F 1 =
2F 2. This aids the interpretation of the contour plot, especially for larger molecules with a complex
carbon skeleton. The number of doublets corresponding to a particular^13 C line in the 1-D spectrum,
which are aligned vertically, is determined by how many other^13 C nuclei are directly bonded to it.
Thus, for a terminal methyl group only one doublet will be observed while methylene, methine and
quaternary carbons can have a maximum of two, three or four doublets respectively, depending on the
structure. The 2-D INADEQUATE spectrum of geraniol is shown in Figure 9.47.