Organic Chemistry

554 CHAPTER 14 NMR Spectroscopy

indicate the presence of an ethyl group that is attached to an electron-withdrawing group.

The signals in the 7.4–8.0 ppm region confirm the presence of a benzene ring. From this

information, we can conclude that the compound is the following ketone. The integration

ratio confirms this answer.

Now continue on to Problem 29.

PROBLEM 29

Identify the compound with molecular formula that gives the IR and

spectra shown in Figure 14.23.

C 8 H 10 O 1 H NMR

CCH 2 CH 3

O

1 5:2:3 2

2.52.6 2.7 2.8 2.9 3 3.5 4 4.5 5 5.5 6 7 8 9 10 11 12 13 14 15 16

4000380036003400320030002800260024002200 2000 1800 1600 1400 1200 1000 800 600

Wavelength (μm)

Wavenumber (cm−^1 )

% Transmittance

87654 3210

δ (ppm)

frequency

Figure 14.23

IR and 1 HNMR spectra for Problem 29.

14.13 Splitting Diagrams

The splitting pattern obtained when a signal is split by more than one set of protons can

best be understood by using a splitting diagram. In a splitting diagram(also called a

splitting tree), the NMR peaks are shown as vertical lines and the effect of each of the

splittings is shown one at a time. For example, a splitting diagram is shown in

Figure 14.24 for splitting of the signal for the proton of 1,1,2-trichloro-3-methylbu-

tane into a doublet of doublets by the Hband Hdprotons.

Hc