Organic Chemistry

576 CHAPTER 14 NMR Spectroscopy

45. Determine the ratios of the chemically nonequivalent protons in a compound if the steps of the integration curves measure 40.5, 27,
    13, and 118 mm, from left to right across the spectrum. Give the structure of a compound whose NMR spectrum would show
    these integrals in the observed order.


46. How could NMR distinguish between the compounds in each of the following pairs?

a. f.

b. g.

c. h.

d. i.

e.

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


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

87654 3210

a.

δ (ppm)

frequency

1 H C 4 H 9 Br

CH 3 CCH 3 and

CH 3

CH 3

CH 2 CCH 3

CH 3

CH 3

and

H

Cl Cl

HH

Cl H

Cl

O

CH 3 C C OCH 3 and

CH 3

CH 3

CH 3 C CH 3

OCH 3

OCH 3

Cl

Cl

H CH 3 and

DH

Cl

Cl

D CH 3

HH

CH 3 CH CHCH 3 and

CH 3 CH 3

CH 3 CCH 2 CH 3

CH 3

CH 3

CH 3 CHCl and

CH 3

CH 3 CDCl

CH 3

BrCH 2 CH 2 CH 2 Br and BrCH 2 CH 2 CH 2 NO 2

CH 3 CH 2 CH 2 OCH 3 and CH 3 CH 2 OCH 2 CH 3 and

1 H

1 H