ChemActivity 16 Spectroscopy 143 Spectroscopy Part C: H NMR (What can a \'H NMR

Question

ChemActivity 16 Spectroscopy 143 Spectroscopy Part C: H NMR (What can a 'H NMR spectrum tell you about the structure of a molecule?) Model 5: H NMR ("Proton NMR") In 'c NMR the signals are generated by carbon nuclei. 'H NMR signals are generated by hydrogen nuclei. (Note that most H NMR peaks appear in the 0-10 ppm range, while most C NMR peaks appear in the 0-220 ppm range.) Figure 5: 'H NMR Spectrum The peak at 0 ppm is a reference peak. It is not associated with any H on the structure shown. proportional peak cluster b of area under solid curve (integration line) . solid curve Critical Thinking Questions 19. How many chemically distinct H's and C's are there on the structure in Figure 5? 20. How many different peak clusters are associated with the structure in Figure 5? 21. Complete the following sentence: In a proton NMR spectrum there is a peak cluster for each chemically distinct H or C [circle one]. 22. On a proton NMR spectrum, the chemical shift (ppm/placement along the x axis) conveys similar information as in C NMR. Construct an explanation for why peak cluster a is farther to the left (higher ppm) than peak cluster b. 23. The dotted line stepping up from Area-0 at the left is a cumulative measure of the integrated area under the solid curve. This is called the integration line. Draw a double-headed arrow with a length proportional to the area of peak cluster a. Which peak cluster a or b [circle one] has a larger area? How you can tell? What is the closest integer ratio 1:1, 1:2, 1:3, 2:3, 3:4 [circle one] that describes the (area of peak cluster a) : (area of peak cluster b)? a) b) c)

Explanation / Answer

19. There are two chemically distinct protonsin 1H NMR figure 5. These protons are identical i.e., they can’t be distinguished from each other based on relative position in the magnetic environment.

Further, there are Three distinct carbon. The acyl, methylene and methyl carbon.

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