N
X
C
Hal
O
N
S
P Si
Natural
Products
Solvents
C
C
C
C C
C
199 199
δ H-2 = 8.59 + Z i2
δ H-3 = 7.25 + Z i3
δ H-4 = 7.62 + Z i4
δ H-5 = 7.25 + Z i5
δ H-6 = 8.59 + Z i 6
Effect of Substituents on the 1 H Chemical Shifts of Monosubstituted Pyridines
(in ppm)
H 3
H 4
H 5
H 6
Substituent
in position 2 or 6
Z 23
Z 65
Z 24
Z 63
Z 25
Z 63
Z 26
Z 62
–CH 3
-0.11
-0.08
-0.15
-0.11
–CH 2 CH 3
-0.09
0.01
-0.15
0.03
–CH 2 –phenyl
0.03
-0.06
0.04
-0.04
–CH 2 OH
0.14
0.03
-0.08
-0.14
–CH=CH 2
-0.07
-0.14
-0.23
-0.12
–phenyl
0.42
0.02
-0.09
0.07
–2-pyridyl
1.27
0.04
-0.11
0.00
–F
-0.30
0.16
-0.05
-0.36
–Cl
0.09
0.02
0.00
-0.10
–Br
0.26
-0.06
0.03
-0.23
–I
0.49
-0.29
0.04
-0.23
–OH*
-0.63
-0.13
-0.93
-1.17
–OCH 3
-0.51
-0.10
-0.41
-0.43
–NH 2
-0.76
-0.24
-0.63
-0.54
–NHCH 2 CH 3
-0.87
-0.22
-0.69
-0.52
–N(CH 3 ) 2
-0.77
-0.23
-0.73
-0.44
–NHNH 2
-0.55
-0.17
-0.58
-0.48
–NHCOCH 3
1.00
0.09
-0.19
-0.32
–NHN=CH–2-pyridyl
0.21
-0.01
-0.42
-0.36
–NO 2
0.93
0.44
0.45
0.00
–C– – – N
0.52
0.26
0.35
0.15
–SH
0.34
-0.20
-0.42
-0.91
–CHO
0.73
0.26
0.31
0.21
–COCH 3
0.80
0.22
0.24
0.10
–CO–phenyl
0.81
0.27
0.25
0.13
–COOH
0.87
0.41
0.44
0.17
–COOCH 3
0.91
0.24
0.27
0.17
–CONH 2
0.98
0.24
0.22
-0.01
–CH=N–NH–2-pyridyl
0.76
0.05
-0.06
-0.03
–Si(CH 3 ) 3
0.15
-0.22
-0.24
0.09
* Keto form (2-pyridone)
C
X
O
N
S
O
||
C
Si
2
3
4
6
5
N
5.6 Heteroaromatic Compounds