Organic Chemistry

Section 14.11 More Examples of^1 HNMR Spectra 549

ethylbenzene ( is a doublet, is a triplet, and is a doublet of doublets). The
nitro group is sufficiently electron withdrawing to cause the and protons to
be in different enough environments that their signals do not overlap.
Notice that the signals for the benzene ring protons in Figures 14.18 and 14.19
occur in the 7.0–8.5 ppm region. Other kinds of protons usually do not resonate in this
region, so signals in this region of an spectrum indicate that the compound
probably contains an aromatic ring.

PROBLEM 21

Explain why the signal for the protons identified as in Figure 14.19 appears at the

lowest frequency and the signal for the protons identified as appears at the highest

frequency. (Hint:Draw the contributing resonance structures.)

PROBLEM 22

How could spectra distinguish the following compounds?

PROBLEM 23

How would the spectra for the four compounds with molecular formula

differ?

PROBLEM 24

Identify each compound from its molecular formula and its 1 H NMRspectrum:

C 3 H 6 Br 2

1 H NMR

NO 2 NO 2 NO 2

Br

Br

Br

AB C

1 H NMR

Hc

Ha

1 H NMR

Ha, Hb, Hc

Hc Hb Ha

10 9 8765 4 3210

a.C 9 H 12

δ (ppm)

frequency

Tutorial:

NMR spectrum assignment