N
X
C
Hal
O
N
S
P Si
Natural
Products
Solvents
C
C
C
C C
C
233
5.11 Carbonyl Compounds
233
Amides of Aliphatic Carboxylic Acids (δ in ppm, J in Hz)
In monosubstituted acetamides, the substituent of the only observable conformer is
cis to the carbonyl oxygen. In disubstituted acetamides, the more stable conformer
has the larger substituent cis to the carbonyl oxygen.
O
N
H
≈2.0
O
N
H
0.96
O
N
H
O
N
H
O
N
O
N
H
O
N
H
H
a
a
a
a
a
H
O
NH
H
O
N
H
H
O
N
H
H
O
N
H
H
O
N
H
O
N
H
O
N
6.6
8.00
8.06
3.34
8.69
8.40
7.14
7.55
7.15
7.33
8.34
7.09
7.37
7.21
3 J HCNH 10.6
3 J HCNH ≈0
1.98
1.98
1.49 0.92
≈2.0
≈2.0
6.7
7.05
7.3
8.1
3.26
3.21 1.35
1.13
1.28
2.08
2.94
3.01
4.01
3.18
1.14
1.55
3.32
1.14
1.20
3 J bc 4.8
8.13
3.32
4.12
1.19
2.83
2.71
4.78
1.10
1.17
6.6
3.30
1.21
≈ 70%
≈ 35%
≈ 30%
≈ 65%
O
N
H
CDCl 3 DMSO
a 2.03
1.76
b 5.42
7.30
c 5.42
6.70
CDCl 3 DMSO
a 1.98
1.78
b 5.53
7.70
c 2.80
2.50
CDCl 3 DMSO
a 1.17
0.97
b 2.26
2.04
c 5.38
7.16
d 6.14
6.62
b
b
b
b
b
c
c
d
c
O
N
H
H
3 J ab 5.9
3 J ab 8.4