N
X
C
O
N
S
Hal
Solvents
Natural
Products
P Si
C
C
C C
C
C
142
4 13 C NMR
4.11.5 Amides and Lactams
Additivity Rule for Estimating the 13 C Chemical Shifts of Amide
Carbon Atoms (δ in ppm)
δ C=O = 166.0 + ∑ Z i
–C γ –C β –C α –CO–N
/
\
C α' –C β'
Substituent i
Z α
Z β
Z γ
Z α'
Z β'
–C
7.7
4.5
-0.7
-1.5
-0.3
–CH=CH 2
3.3
–phenyl
4.7
-4.5
13 C Chemical Shifts of Amides (δ in ppm)
Formamides:
Primary and Secondary Acetamides:
C α' –C β'
H 3 C
O
N
H
H 3 C
O
N
H
CH 3
H 3 C
O
NH 2
H
O
N
CH 3
CH 3
H
O
NH
CH 3
H
O
N
H
CH 3
H
O
N
H
O
NH
H
O
NH 2
167.6
161.8
173.4*
164.9
171.7
171.0
162.6
163.3
166.5
162.6
24.8
28.2
≈ 90%
≈ 10%
≈ 90%
≈ 10%
* in water: 177.0
36.5
31.5
H
O
N
H
33.0
14.6
22.3
22.7
22.8
26.1
14.6
34.4
16.8
14.9
12.8
36.9
41.9
36.7