Organic Chemistry

Section 14.13 Splitting Diagrams 555

The signal for the protons of propyl bromide is split into a quartet by the protons,
and each of the resulting four peaks is split into a triplet by the protons (Figure 14.25).
How many of the 12 peaks are actually seen depends on the relative magnitudes of the two
coupling constants, and For example, the figure shows that there are 12 peaks
when is much greater than 9 peaks when and only 6 peaks when
As you can see, the number of peaks actually observed depends on how many
overlap with one another. When peaks overlap, their intensities add together.

Jba=Jbc.

Jba Jbc, Jba= 2 Jbc,

Jba Jbc.

Hc

Hb Ha

CH 3

CH 3 CHCHCHCl

ClCl

1,1,2-trichloro-3-methylbutane

a doublet of doublets

chemical shift of the signal for the

Hc proton if there were no splitting

splitting by the Hb proton

a splitting diagram

ab

c d

splitting by the Hd proton

Jcd Jcd

Jcb

Hc

frequency

>Figure 14.24

A splitting diagram for a doublet of

doublets.

propyl bromide

12 peaks 9 peaks 6 peaks

CH 3 CH 2 CH 2 Br

acb

Jbc

Jba

Jba >> Jbc Jba = 2 Jbc Jba = Jbc

Hb Hb Hb

Jbc

Jba

Jbc

Jba

Figure 14.25
A splitting diagram for a quartet of triplets. The number of peaks actually observed when
a signal is split by two sets of protons depends on the relative magnitudes of the two
coupling constants.