N
X
C
Hal
O
N
S
P Si
Natural
Products
Solvents
C
C
C
C C
C
4.2 Alkenes
87
Example: Estimation of chemical shifts of cis-4-methyl-2-pentene
a base value
123.3
b base value
123.3
1 α-C
10.6
1 α-C
10.6
1 α'-C
-7.9
2 β-C
9.8
2 β'-C
-3.6
1 α'-C
-7.9
cis-α,α'
-1.1
cis-α,α'
-1.1
estimated
121.3
1 β-substituent
2.3
exp
121.8
estimated
137.0
exp
138.8
Effect of Substituents on the 13 C Chemical Shifts of Vinyl Compounds (δ in
ppm)
δ C i
= 123.3 + Z i
Substituent R
Z 1
Z 2
–H
0.0
0.0
–CH 3
12.9
-7.4
–CH 2 CH 3
17.2
-9.8
–CH 2 CH 2 CH 3
15.7
-8.8
–CH(CH 3 ) 2
22.7 -12.0
–(CH 2 ) 3 –
14.6
-8.9
–C(CH 3 ) 3
26.0 -14.8
–CH 2 Cl
10.2
-6.0
–CH 2 Br
10.9
-4.5
–CH 2 I
14.2
-4.0
–CH 2 OH
14.2
-8.4
–CH 2 OCH 2 CH 3 12.3
-8.8
–CH=CH 2
13.6
-7.0
–C– – – CH
-6.0
5.9
–phenyl
12.5 -11.0
–F
24.9 -34.3
–Cl
2.8
-6.1
–Br
-8.6
-0.9
–I
-38.1
7.0
Substituent R
Z 1
Z 2
–OH
25.7 -35.3
–OCH 3
29.4 -38.9
–OCH 2 CH 3
28.8 -37.1
–O(CH 2 ) 3 CH 3
28.1 -40.4
–OCOCH 3
18.4 -26.7
–N(CH 3 ) 2
21.2 -41.5
–N + (CH 3 ) 3
19.8 -10.6
–N-pyrrolidonyl
6.5 -29.2
–NO 2
22.3
-0.9
–C– – – N
-15.1
14.2
–NC
-3.9
-2.7
–SCH 2 CH 3
9.0 -12.8
–S(O) 2 CH=CH 2 14.3
7.9
–CHO
15.3
14.5
–COCH 3
13.8
4.7
–COOH
5.0
9.8
–COOCH 2 CH 3
6.3
7.0
–COCl
8.1
14.0
–Si(CH 3 ) 3
16.9
6.7
–SiCl 3
8.7
16.1
a
b
1
2
O
N
S
O
||
C
Si
C
X
CH CH 2
R