NMR Spectroscopy

13C Chemical Shift Calculations for Substituted Benzene Rings

dC = 128.5 + Sdi
Substituent (R) dipso dortho dmeta dpara
-Me 9.3 0.7 -0.1 -2.9
-Et 15.6 -0.5 0 -2.6
-nPr 14.2 -0.2 -0.2 -2.8
-iPr 20.1 -2.0 0 -2.5
-tBu 22.2 -3.4 -0.4 -3.1
-CH=CH2 9.1 -2.4 0.2 -0.5
-CCH -5.8 6.9 0.1 0.4
-C6H5 12.1 -1.8 -0.1 -1.6
-CH2Cl 9.1 0 0.2 -0.2
-CH2OH 13.0 -1.4 0 -1.2
-CHO 8.2 1.2 0.6 5.8
-C(O)R 7.8 -0.4 -0.4 2.8
-C(O)C6H5 9.1 1.5 -0.2 3.8
-CO2H 2.9 1.3 0.4 4.3
-CO2R 2.0 1.2 -0.1 4.8
-CN -16.0 3.6 0.6 4.3
-NH2 19.2 -12.4 1.3 -9.5
-NR2 22.4 -15.7 0.8 -11.8
-NHC(O)R 11.0 -9.9 0.2 -5.6
-NO2 19.6 -5.3 0.9 6.0
-OH 26.6 -12.7 1.6 -7.3
-OCH3 31.4 -14.4 1.0 -7.7
-OC(O)R 22.4 -7.1 -0.4 -3.2
-F 35.1 -14.3 0.9 -4.5
-Cl 6.4 0.2 1.0 -2.0
-Br -5.4 3.4 2.2 -1.0
-I -32.2 9.9 2.6 -7.3
-SiR3 13.4 4.4 -1.1 -1.1
-PPh2 8.7 5.1 -0.1 0
-SR 9.9 -2.0 0.1 -3.7

Example 1:

dC1,3,5 = 128.5 + 9.3 + (-0.1) + (-0.1) = 137.6 ppm
Observed: 137.4 ppm
dC2,4,6 = 128.5 + 0.7 + 0.7 + (-2.9) = 127.0 ppm
Observed: 127.0 ppm

Example 2:

dC1 = 128.5 + 8.2 + (-12.7) = 124.0 ppm
Observed: 121.0 ppm
dC2 = 128.5 + 26.6 + 1.2 = 156.3 ppm
Observed: 161.4 ppm
dC3 = 128.5 + (-12.7) + 0.6 = 116.4 ppm
Observed: 117.4 ppm
dC4 = 128.5 + 1.6 + 5.8 = 135.9 ppm
Observed: 136.6 ppm
dC5 = 128.5 + (-7.3) + 0.6 = 121.8 ppm
Observed: 119.6 ppm
dC6 = 128.5 + 1.2 + 1.6 = 131.3 ppm
Observed: 133.6 ppm

Return to: NMR Spectroscopy Page