Analysis of NMR of cholesterol

cholesterol -


Figure_1.1.jpg
Figure 1.1: HNMR spectrum of cholesterol.[this image is not cholesterol JCB]



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Figure 1.2: a single peak is observed at 7.2ppm. This represents the residual peak of CHCl3 from CDCl3 solvent.



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Figure 1.3: at 5.35-5.36ppm, a doublet of doublets can be expected which corresponds to the coupling of the H-atom (bonded to the sp2 C-atom inside the central ring of the cholesterol molecule) with the H-atoms on the adjacent CH2. The H-atoms on the adjacent CH2 group are acting differently due to chirality of the cholesterol molecule. In other words, it is acting diastereotopically. Notice the actual NMR does not perfectly illustrate four peaks as would be expected with a doublet of doublets. This may be due to error in the spectrum.
Figure_1.4.jpg
Figure 1.4: Because of the H-atom directly attached to the oxygen group on the cholesterol molecule, a multiplet can be expected from 2-5ppm [no you are mixing up ranges JCB], although there really is no wrong range for H-bonded groups. Additionally, 16 peaks can be expected because extensive coupling occurs (a doublet of a doublet of a doublet of a doublet). Several peaks are observed at 3.5ppm on the spectrum. Although not exactly 16 peaks occur, this is still consistent with the cholesterol molecule because peaks may be hidden within other peaks.



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Figure 1.5: Two doublets are observed at .85 and .87ppm, respectively. These peaks correspond to the H-atoms attached to the the external CH3 groups on the cholesterol molecule. These groups exhibit diastereotopicity and therefore act differently to generate four peaks.



Figure_1.6.jpg
Figure 1.6: Displays a zoomed out version of the four peaks illustrated in Figure 1.7. This view also depicts a single peak at .7ppm which most likely corresponds to the H-atom attached to the CH3 side group located in between the ring system of the cholesterol molecule. Additionally, a similar CH3 side group can be visualized inside the more internally located ring system and is illustrated in Figure 1.7.



Figure_1.7.jpg
Figure 1.7: Another singlet is observed at 1.02ppm, corresponding to the additional CH3 side group mentioned in Figure 1.6. It is important to note that it is not known which singlet corresponds exactly to each of the sp3 hybridized methyl groups. The singlets illustrated in Figures 1.6 and 1.7 were assigned randomly and could correspond to either of the methyl groups located inside the ring system of the cholesterol molecule.



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Figure 1.8: Extensive coupling is observed corresponding to the remaining H-atoms found throughout the cholesterol molecule.



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Figure 1.9: Extensive coupling is observed corresponding to the remaining H-atoms found throughout the cholesterol molecule.



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Figure 1.10: Extensive coupling is observed corresponding to the remaining H-atoms found throughout the cholesterol molecule.

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