By Zahf Shaikh


Figure 1- H NMR spectra for caffeine

Figure 2- In this figure, three singlets are observed. The first peak between 3.15-3.30 represents the hydrogens on the methyl group that is connected to the single bonded nitrogen. The peak between 3.30-3.45 represents the hydrogens proton of the methyl group next to the double bonded oxygen and double bonded carbon. The third peak between 3.75-3.90 represents the hydrogen protons present on the methyl group between the two carbons with the double bonded oxygen. The deshielding due to the nitrogens near all the hydrogens causes the shift in the spectra. This is most evident in the third peak because the hydrogens are located near a carbon that is attached to a nitrogen near two carbons with double bonded oxygens.
Figure 3- In this figure, one peak is observed due to the solvent used to conduct the H NMR. A D2O was used and caused this large peak between 4.800-4.880.

Figure 4- In this figure, one peak is observed due to the hydrogen proton located on the carbon between the two nitrogen groups. The deshielding due to the carbons are located next to nitrogen that cause a great shift in the spectra. After checking the intergration data, it is apparent that one hydrogen is represented by this peak.

[Reasonable guess of the assignments but we can't be completely sure till we compare with similar compounds JCB]

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