Nuclear Magnetic Resonance Spectroscopy: Theory and Applications
491
C
H
F
C C
F H
F
F
H
H
H
a
b
c
splitting
splitting
weak splitting
splitting
weak splitting
No splitting
Coupling constant between fluorine cover a wider splitting range than
1 H NMR.
Some examples of 1 H and 19 F NMR.
Example 1,
H 3 C C F
H
Br
a
b
c
H a
H 3 C C F
H
Br
a
b
c
Ha-Hb
2nI + 1= 2x3x1/2 + 1= 4
Ha-Fc
2nI + 1= 2x1x1/2 + 1= 2
H b
Hb-Ha
2nI + 1= 2x1x1/2 + 1= 2
Ha-Fc
2nI + 1= 2x1x1/2 + 1= 2
H 3 C C F
H
Br
a
b
c
F c
H 3 C C F
H
Br
a
b
c
Fc-Ha
2nI + 1= 2x1x1/2 + 1= 2
Fc-Hb
2nI + 1= 2x3x1/2 + 1= 4
1 H NMR
19 F NMR
doublets of quatrets
8 lines
double doublets
4 lines
quatrets of doublets
8 lines
Example 2,
H 3 C C
O
CH 2
a
b c
F
1 H NMR
19 F NMR
H 3 C C
O
CH 2
a
b c
F
H 3 C C
O
CH 2
a
b c
F
H 3 C C
O
CH 2
a
b c
F
H b
Hb-Ha
2nI + 1= 2x1x1/2 + 1= 2
doublets
2 lines
doublets
2 lines
LONG RANGE COUPLING
H a
F c
Fc-Ha
2nI + 1= 2x2x1/2 + 1= 3
Fc-Hb
2nI + 1= 2x3x1/2 + 1= 4
quatrets of triplets
12 lines