N
X
C
O
N
S
Hal
Solvents
Natural
Products
P Si
C
C
C C
C
C
138
4 13 C NMR
13 C Chemical Shifts of Diketones (δ in ppm)
4.11.3 Carboxylic Acids
Additivity Rule for Estimating the 13 C Chemical Shifts of Carboxyl
Carbon Atoms (δ in ppm)
δ C=O = 166.0 + ∑ Z i
–C γ –C β –C α –COOH
Substituent i
Z α
Z β
Z γ
–C
12.0
3.0
-1.0
–CH=CH 2
5.0
0.5
-1.5
–phenyl
6.0
1.0
-2.0
13 C Chemical Shifts of Carboxylic Acids (δ in ppm)
H 3 C
O
CH 3
O
H 3 C
O
CH 3
O
H 3 C
CH 3
O
O
COOH
23.2
28.5
29.6
56.6
37.0
Enol form: see Chapter 4.8.1
197.7
201.1
206.9
H COOH
COOH
COOH
COOH
COOH
COOH
COOH
COOH
COOH
COOH
20.8
18.8
14.2
22.7
74.0
78.6
43.7
29.6
26.2
26.6
27.7
34.8
38.7
47.9
27.0
29.6
30.6
34.1
27.6
18.4
36.2
13.6
8.9
166.3
184.1
172.0
133.2 128.1
156.5
130.6
130.1
128.4
133.7
182.1
172.6
180.6
185.9
179.4
178.1
181.5
180.7
COOH
H 3 C