C-13 NMR Spectroscopy
CHM 320
La Salle University
C-13 NMR Spectroscopy
CHM 320
La Salle University
C-13 Spectrum of
m-Nitroacetophenone
NO
2
CCH
3
O
1H NMR Spectrum of
Ethylbenzene
CH
2
CH
3
Typical ppm ()Ranges in
C-13 NMR
Relaxation Times
Coupling Constants are
Large
J Values measured in Hz
HC
CCH
2
CH
2
CH
2
CH
3
HC
CCH
2
CH
2
CH
2
CH
3
CH
3
CH
2
OCCH
2
CCH
3
O
O
CH
3
CH
2
OCCH
2
CCH
3
O
O
H
2
C=C=CHCH
2
CH
2
OH
CO
2
H
N
H
3
C
H
3
C
CCH
3
O
Silverstein, p. 212
N
H
3
C
H
3
C
CH
OCH
3
OCH
3
C
C
H
NHCCH
3
O
H
3
C
HC
O
CF
3
COCH
3
O
Predicting Chemical
Shifts
Predicted Chemical Shifts
of
C
a
and
C
b
a
b
C
a
= (-2.5) + 4(9.1) + 9.4 + 2(-2.5) + 3(-1.5) + (-8.4) =
25.4 ppm
C
b
= (-2.5) + 2(9.1) + 5(9.4) +(-7.2) + (-2.5) =
53.0 ppm
base
4
o
(1
o
) 4
o
(2
o
)
base
2
o
(4
o
) 2
o
(3
o
)
2,2,4-Trimethylpentane
53.28, 31.10, 30.16, 25.51,
24.73
Chemical Shift
Prediction with
Functional Groups
Use Base Value From
Table 4.5
OH
OH
OH
Using Table 4.5 and 4.6
34.7 + 41 = 75.7
22.8 + 41 = 63.8
13.9 + 48 = 51.9 ppm
You can Choose Which
Base Value from Table
4.5 to Use
OH
OH
34.7 + 41 + (-5) + 3(9.4) + (-2.5) + (-7.2) =
89.2 ppm
C-3 -OH -OH
2
o
(3
o
) 2
o
(4
o
)
OH
OH
36.9 + 41 + (-5) + 2(9.4) + (-2.5) =
88.8 ppm
C-3 -OH -OH
2
o
(3
o
)
Spectrum at 75 MHz and
150 MHz
