N
X
C
O
N
S
Hal
Solvents
Natural
Products
P Si
C
C
C C
C
C
164
4 13 C NMR
164
4 13 C NMR
4.14.2 13 C NMR Spectra of Secondary Reference Compounds
Chemical shifts in 13 C NMR spectra are usually reported relative to the peak position of tetramethylsilane (TMS), which is added as an internal reference. If TMS is
not sufficiently soluble in the sample, the use of a capillary with TMS as external
reference is recommended. In this case, owing to the difference in volume susceptibilities, the local magnetic fields in the solvent and reference are different.
Therefore, the position of the reference must be corrected. For a D 2 O solution in
a cylindrical sample with TMS in a capillary, the correction amounts to +0.68 and
-0.34 ppm for superconducting and electromagnets, respectively. These values must
be added to the 13 C chemical shifts relative to the external TMS signal if its position
is set to 0.00 ppm. Alternatively, secondary references with (CH 3 ) 3 SiCH 2 groups
may be used. The following spectra of two secondary reference compounds in D 2 O
were measured at 125 MHz with a superconducting magnet and TMS as external
reference. Chemical shifts are reported in ppm relative to TMS upon correction for
the difference in the volume susceptibilities of D 2 O. As a result, the peak for the
external TMS appears at 0.68 ppm.
3-(Trimethylsilyl)-1-propanesulfonic acid sodium salt (sodium 4,4-dimethyl-4silapentane-1-sulfonate; DSS)
200
180
160
140
120
100
80
60
40
20
0
55.1
19.8
-1.9
15.8
0.68 TMS
(external reference)
Si
SO 3 Na
H 3 C CH 3
H 3 C
2,2,3,3-D 4 -3-(Trimethylsilyl)-propionic acid sodium salt
200
180
160
140
120
100
80
60
40
20
0
187 186 33
32
31
13
12
186.3
12.7
31.9
-2.0
0.68 TMS
(external reference)
Si
COONa
H 3 C
H 3 C
H 3 C D D
D
D
X
C
O
N
S
Hal
Solvents
Natural
Products
P Si
C
C
C C
C
C
164
4 13 C NMR
164
4 13 C NMR
4.14.2 13 C NMR Spectra of Secondary Reference Compounds
Chemical shifts in 13 C NMR spectra are usually reported relative to the peak position of tetramethylsilane (TMS), which is added as an internal reference. If TMS is
not sufficiently soluble in the sample, the use of a capillary with TMS as external
reference is recommended. In this case, owing to the difference in volume susceptibilities, the local magnetic fields in the solvent and reference are different.
Therefore, the position of the reference must be corrected. For a D 2 O solution in
a cylindrical sample with TMS in a capillary, the correction amounts to +0.68 and
-0.34 ppm for superconducting and electromagnets, respectively. These values must
be added to the 13 C chemical shifts relative to the external TMS signal if its position
is set to 0.00 ppm. Alternatively, secondary references with (CH 3 ) 3 SiCH 2 groups
may be used. The following spectra of two secondary reference compounds in D 2 O
were measured at 125 MHz with a superconducting magnet and TMS as external
reference. Chemical shifts are reported in ppm relative to TMS upon correction for
the difference in the volume susceptibilities of D 2 O. As a result, the peak for the
external TMS appears at 0.68 ppm.
3-(Trimethylsilyl)-1-propanesulfonic acid sodium salt (sodium 4,4-dimethyl-4silapentane-1-sulfonate; DSS)
200
180
160
140
120
100
80
60
40
20
0
55.1
19.8
-1.9
15.8
0.68 TMS
(external reference)
Si
SO 3 Na
H 3 C CH 3
H 3 C
2,2,3,3-D 4 -3-(Trimethylsilyl)-propionic acid sodium salt
200
180
160
140
120
100
80
60
40
20
0
187 186 33
32
31
13
12
186.3
12.7
31.9
-2.0
0.68 TMS
(external reference)
Si
COONa
H 3 C
H 3 C
H 3 C D D
D
D