Organic Chemistry

568 CHAPTER 14 NMR Spectroscopy

14.19 DEPT NMR SPECTRA

A technique called DEPT NMR has been developed to distinguish among

and CH groups. (DEPT stands for distortionless enhancement by polarization

transfer.) It is now much more widely used than proton coupling to determine the

number of hydrogens attached to a carbon.

The of citronellal is shown in Figure 14.36. A DEPT

NMR shows four spectra of the same compound. The bottommost spectrum shows signals

for all carbons that are covalently bonded to hydrogens.The next-to-the-bottom spectrum

is run under conditions that allow only signals resulting from CH carbons to appear. The

third spectrum is run under conditions that allow only signals produced by carbons to

appear, and the top spectrum shows only signals produced by CH 3 carbons. Information

CH 2

DEPT 13 C NMR spectrum^13 C

CH 2 ,

13 C CH 3 ,

(^13) C
200 175 150 125 100 75 50 25 0
Intensity
d.C 6 H 12
δ (ppm)
frequency
CO
H
ppm
CH 3 carbons
CH 2 carbons
CH carbons
all protonated carbons
200 180 160 140 120 100 80 60 40 20 0
Figure 14.36N
DEPT spectrum of
citronellal.
13 C NMR
Figure 14.35 (continued)
The^13 C NMRspectra for Problem 39.