N
X
C
Hal
O
N
S
P Si
Natural
Products
Solvents
C
C
C
C C
C
4.9 Nitrogen Compounds
123
4.9 Nitrogen Compounds
4.9.1 Amines
13 C Chemical Shifts of Amines and Ammonium Salts (δ in ppm)
The protonation of amines causes a shielding of the carbon atoms in the vicinity of
the nitrogen. This shielding amounts to -2 ppm for an α carbon atom, -3 to -4 for a
β carbon, and -0.5 to -1.0 ppm for a γ carbon. The most frequent exceptions occur
in branched systems: Tertiary and quaternary carbon atoms in the α-position are
generally deshielded by protonation of the nitrogen (Δδ = +0.5 to +9 ppm). In the
following, shifts induced by protonation (δ amine hydrochloride - δ amine , measured in
D 2 O) are given in parentheses.
H 3 C
N
H 3 C
CH 3
H 3 C
NH
H 3 C
N
HO
OH
HO
N
+
I
-
H 3 C NH 2
NH
HO
HO
NH 2
NH 2
NH
NH
N
N
N
+
I
-
NH 2
NH 2
H
N
28.3 (-1.8)
19.0 (-5.0)
36.9 (-0.2)
15.7
(-3.2)
11.5
(-0.4)
26.5
(-4.9)
64.2
(-5.4)
60.3
(-3.5)
44.6
(-1.9)
57.4
(-1.0)
32.9
(-4.7)
47.2
(+5.7)
43.0
(+2.2)
12.9
(-1.7)
44.5
(-0.6)
44.6
(-1.8)
12.0
(-0.5)
52.4
(-1.4)
24.0
(-2.6)
27.4
(-5.4)
51.4
(+1.3)
38.2 (-2.0)
47.6 (-1.2)
56.5
55.4
45.7
(in D 2 O)
22.8
60.5
51.3
56.8
21.3
10.9
12.0
16.0
60.4
9.5
NH 2
HO
(CH 3 ) 4 N
+
I
–