Organic Chemistry

Section 14.11 More Examples of^1 HNMR Spectra 545

a.

b.

10 9 8765 4 3 210

Offset: 1.7 ppm.

10 9 8765 4 3 210

Offset: 2.4 ppm.

δ (ppm)

frequency

δ (ppm)

frequency

3.9 3.8 3.7PPM 3.0 2.9 2.8 PPM

4.6 4.5 4.4

1.9 1.8 1.7 1.6

PPM

PPM

Figure 14.14

1 HNMR spectra for Problem 19.

PROBLEM 18

Using a diagram like the one in Figure 14.13, predict

a. the relative intensities of the peaks in a triplet

b. the relative intensities of the peaks in a quintet

PROBLEM 19

The NMR spectra of two carboxylic acids with molecular formula are

shown in Figure 14.14. Identify the carboxylic acids. (The “offset”notation means that the

signal has been moved to the right by the indicated amount).

1 H C 3 H 5 O 2 Cl

14.11 More Examples of NMR Spectra

The NMR spectrum of bromomethane shows one singlet. The three methyl protons
are chemically equivalent, and chemically equivalent protons do not split each other’s
signal. The four protons in 1,2-dichloroethane are also chemically equivalent, so its
NMR spectrum also shows one singlet.

bromomethane

each compound has an NMR spectrum that shows one singlet

because equivalent protons do not split each other‘s signals

CH 3 Br

1,2-dichloroethane

ClCH 2 CH 2 Cl

1 H

1 H

(^1) H