N
X
C
O
N
S
Hal
Solvents
Natural
Products
P Si
C
C
C C
C
C
140
4 13 C NMR
4.11.4 Esters and Lactones
Additivity Rule for Estimating the 13 C Chemical Shifts of Ester Carbon Atoms (δ in ppm)
δ C=O = 166.0 + ∑ Z i
–C γ –C β –C α –COO–C α' –
Substituent i
Z α
Z β
Z γ
Z α'
–C
12.0
3.0
-1.0
-5.0
–CH=CH 2
5.0
-9.0
–phenyl
6.0
1.0
-8.0
13 C Chemical Shifts of Acetic Acid Esters (δ in ppm)
13 C Chemical Shifts of Methyl Esters (δ in ppm)
O
O
CH 3
O
O
CH 3
O
O
CH 3
O
O
CH 3
O
O
CH 3
H 3 C
O
O
CH 3
H
O
O
CH 3
H 3 C
O
O
H 3 C
O
O
H 3 C
O
O
H 3 C
O
O
H 3 C
O
O
H 3 C
O
O
H 3 C
O
O
CH 3
168.0
161.6
171.3
173.3
173.4
177.4
172.2
178.8
171.3
169.2
169.2
97.5
170.7
170.3
170.2
20.6
20.6
49.1
51.5
51.5
51.6
51.5
51.9
51.5
21.0
20.6
27.2
34.9
34.1
23.9
13.8
27.3
38.7
35.6
18.9
9.2
28.5
19.1
15.1
20.8
32.2
121.4
24.4
128.9
26.1
125.3
72.3
150.9
14.4
21.9
28.1
67.5
79.9
20.9
21.3
22.3
51.5
141.4
60.4