N
X
C
O
N
S
Hal
Solvents
Natural
Products
P Si
C
C
C C
C
C
92
4 13 C NMR
4.3.2 Coupling Constants
13 C- 1 H Coupling Constants (|J CH | in Hz) [2]
With acetylenes, the results of multipulse experiments (such as DEPT, INEPT,
SEFT, or APT) to determine the number of protons attached to the carbon atoms
must be interpreted with care. As a consequence of the unusually large 13 C- 1 H coupling constants through one and two bonds, the sign of the signals may be opposite
to the expected one. For the same reasons, unexpected signals may occur in twodimensional heteronuclear correlation spectra (HSQC, HMBC).
13 C- 13 C Coupling Constants (| 1 J CC | in Hz)
4.3.3 References
[1] W. Höbold, R. Radeglia, D. Klose, Inkrementen-Berechnung von 13 C-chemischen Verschiebungen in n-Alkinen, J. Prakt. Chem. 1976, 318, 519.
[2] K. Hayamizu, O. Yamamoto, 13 C, 1 H Spin coupling constants of dimethylacetylene, Org. Magn. Reson. 1980, 13, 460.
H C C H
1 J CC 171.5
1 J ab 190.3
1 J bc 153.4
a
b
c
H C C C C H
H C C H
1 J ab 249.0
2 J ac 49.3 (in substituted acetylenes: 40–60)
2 J ac 50.1
2 J ce -10.4
2 J ab -10.3 3 J ac 4.3
3 J ad 3.4
3 J be 4.7
a
a
a
b
b
b
c
c
c
d e
H 3 C C C CH 3
H C C CH 3