N
X
C
O
N
S
Hal
Solvents
Natural
Products
P Si
C
C
C C
C
C
184
5 1 H NMR
H
O
H
H
H
H
H
H
H
H
H
H
H
H H
H
H
H
H
H
H
H
In condensed alicyclics, couplings over four bonds are often observed. Such longrange couplings are particularly large if the arrangement of the bonds between the
two protons is W-shaped (cf. J ac vs. J ad and J bd below left and J ac vs. J bc below
right).
Owing to the rigid arrangement, vicinal coupling constants ( 3 J) may assume unusually small values when the torsional angles are close to 90° (J ce below right).
6.50
5.79
5.56
1.76
7.90
7.38
8.31
7.12
7.52
1.87
1.34
H
H
H
H
2.00
6.75
3.58
1.12
1.63
6.02
0.98
2.87
6.09
5.59
2.14
1.47
2.11
1.5
1.5
5.26
2.22
4 J ac 2.3
4 J bc -0.1
3 J ce 0.1
3 J de 4.7
3 J ab ≈10
3 J bc 3.7
3 J ab 11.3
3 J aa' 4.1
4 J ab' -0.6
5 J bb' 0.5
4 J ac ≈7
4 J ad ≈0
4 J bd ≈0
a
a
a'
a
b
b
b'
b
d
d
d
f
g
c
c
c
e, e'
e
1.18
2.19
1.47
1.16
1.50 1.50
H
H H
H
6.25
2.48
1.23
1.50
4.60
2.06
1.50
1.82
1.55
1.73
1.47
1.82
2.59
1.84
2.67
6.63
H
H
H
H
a
b
d
c
a
b
d
c
e
3 J ab 11.2
4 J ac 0.8
3 J bc 5.5
3 J cd 8.9
5 J cg -0.6
3 J de 6.7
2 J ee' -13.0
5 J cf = 4 J df = 5 J dg = 0