Chapter 14: NMR Spectroscopy

What does cross peak X in figure tell you?

How many signals are produced by each of the following compounds in its

a.${}^{\mathbf{1}}\mathbf{H}\mathbf{}\mathbf{NMR}\mathbf{}\mathbf{Spectrum}\mathbf{}\mathbf{?}$

b. ${}^{\mathbf{13}}\mathbf{C}\mathbf{}$NMR spectrum?

1.

2.

3.

4.

5.

6.

Draw a splitting diagram for the ${\mathrm{H}}_{\mathrm{b}}$proton and give its multiplicity if

a.${\mathbf{J}}_{\mathrm{ba}}\mathbf{=}{\mathbf{J}}_{\mathrm{bc}}$ b.${\mathbf{J}}_{\mathbf{ba}}\mathbf{=}\mathbf{2}{\mathbf{J}}_{\mathbf{bc}}$

Label each set of chemically equivalent protons, using ‘a’ for the set that will be at the lowest frequency in the ${}^{\mathbf{1}}\mathbf{H}$NMR spectrum, ‘b’ for the next lowest, and so on. Indicate the multiplicity of each signal.

a.

b.

c.

d.

e.

f.

How many signals would you expect to see in the NMR spectrum of each of the following compounds ?

Determine the ratios of the chemically non-equivalent protons in a compound if the steps of the integration curves measure $\mathbf{40}\mathbf{.5}\mathbf{,}\mathbf{27}\mathbf{,}\mathbf{13}$ and$\mathbf{118}\mathbf{mm}$ , from left to right across the spectrum. Draw the structure of a compound whose ${}^{\mathbf{1}}\mathbf{H}$NMR spectrum would show these integrals in the observed order.

How an ${}^{\mathbf{1}}\mathbf{H}$NMR distinguish between the compounds in each of the following pairs?

a.

b.

c.

d.

e.

f.

g.

h.

i.

j.

Answer the following questions:

a. What is the relationship between chemical shift in ppm and operating frequency?

b. What is the relationship between chemical shift in hertz and operating frequency?

c. What is the relationship between coupling constant in hertz and operating frequency?

d. How does the operating frequency in NMR spectroscopy compare with the operating frequency in IR and UV/Vis spectroscopy?

Match each of the ¹HNMR spectra with one of the following compounds:

a.

b.

c.

The ¹H NMR spectra of three isomers with molecular formula C₄H₉Br are shown here. Which isomer produces which spectrum?

a)

b)

c)