N
X
C
O
N
S
Hal
Solvents
Natural
Products
P Si
C
C
C C
C
C
222
5 1 H NMR
1 H Chemical Shifts and Coupling Constants of Isonitriles (δ in ppm,
|J| in Hz)
Because of the symmetrical electron distribution around the N atom, the quadrupole
relaxation of the nitrogen nucleus is so slow that the 14 N- 1 H coupling becomes observable and leads to triplets with relative intensities of 1:1:1 (spin quantum number
of 14 N: I = 1; natural abundance, 99.6%):
5.9.7 Cyanates, Isocyanates, Thiocyanates, and Isothiocyanates
1 H Chemical Shifts and Coupling Constants (δ in ppm, J in Hz)
CH 3 NC
CH 2 CH 2
14
NC
H
H
H
NC
NCS
SCN
NCO
H
H
H
NCO
| 2 J aN | 1.8–2.8
| 3 J bN | 1.5–3.5
a
a
a
a
a
a
a
b
b
b
b
c
c
b
NC
NC
| 2 J aN | 2.3
| 3 J bN | 6.1
| 3 J cN | 3.1
3 J ab 8.6
3 J ac 15.6
2 J bc -0.5
3 J ab 7.6
3 J ac 15.2
2 J bc -0.1
2.85
1.45
1.45
3.02
1.20
1.53
7.15
7.30
7.24
1.40
1.29
2.60
3.37
3.72
3.48
7.4–7.5
3.98
3.37
2.98
3.64
3.26
3.29
0.99
1.42
1.63
1.58
6.12
0.94
4.77
5.01
4.54
3.89
5.35
5.58
5.90
1.28
1.45
3.87
| 2 J aN | 2.3
| 3 J aN | 2.1
| 2 J aN | 1.8
| 3 J bN | 2.6
| 3 J ab | 7.0
| 2 J aN | 2.0
| 3 J bN | 2.4
| 3 J ab | 7.3
OCN
NCO
CH 3 NCO
NCO
NCO
CH 3 SCN
SCN
CH 3 NCS
NCS
NCS
NC
SCN