Jl

C Spectrum V

240 220 200 180 160 140 120 100 80 60 40 20 0 ppm

Figure 6.17

(C5, 140.8 ppm). The other olefinic carbon (C6, 122.0 ppm) is a CH and gives a positive APT peak. The single oxygenated carbon (C3, CHOH at 72.0 ppm) is also positive (CH), as are the three downfield CH carbons (C9, C14 and C17, 50-60 ppm) that are adjacent to sp3-hybridized quaternary carbons (sterically crowded). The upfield region is shown in Figure 6.19, also aligned with the 13C spectrum. The structural assignments (carbon numbers), which are derived from analysis of two-dimensional spectra, are also shown. In the 13C spectrum, there is a peak at 32.0 ppm that represents two overlapped carbons peaks: a CH and a CH2. Because these have slightly different chemical shifts, the opposite sign in the APT spectrum allows them to be clearly resolved. A broad peak at 42.3 ppm in the 13C spectrum represents two peaks that are not resolved: a CH2 and a Cq. These are also

Cholesterol, 43 mg in CDC13

Cholesterol, 43 mg in CDC13

1 1 I 1 1 1 1 I 1 1 1 1 I 1 1 1 1 I 1 1 1 1 I 1 1 1 1 I 1 1 1 1 I 1 1 1 1 I 1 1 1 1 I 1 1 1 1 I 1

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