C-13 NMR Spectroscopy CHM 320 La Salle University

C-13 NMR SpectroscopyCHM 320

La Salle University

C-13 Spectrum ofm-Nitroacetophenone

NO2

CCH3

O

1H NMR Spectrum ofEthylbenzene

CH2CH3

Typical ppm ()Ranges in C-13 NMR

Relaxation Times

Coupling Constants are LargeJ Values measured in Hz

HC CCH2CH2CH2CH3

HC CCH2CH2CH2CH3

CH3CH2OCCH2CCH3

OO

CH3CH2OCCH2CCH3

OO

H2C=C=CHCH2CH2OH

CO2H

NH3C

H3C

CCH3

O

Silverstein, p. 212

Silverstein, p. 215

N

H3C

H3C

CH

OCH3

OCH3

CC

H

NHCCH3

O

H3C

HC

O

CF3COCH3

O

Predicting Chemical Shifts

Predicted Chemical Shifts of Ca and Cb

a

b

Ca = (-2.5) + 4(9.1) + 9.4 + 2(-2.5) + 3(-1.5) + (-8.4) = 25.4 ppm

Cb = (-2.5) + 2(9.1) + 5(9.4) +(-7.2) + (-2.5) = 53.0 ppm

base 4o(1o) 4o(2o)

base 2o(4o) 2o(3o)

2,2,4-Trimethylpentane

53.28, 31.10, 30.16, 25.51, 24.73

Chemical Shift Prediction with Functional Groups

Use Base Value From Table 4.5

OH

OH

OH

Using Table 4.5 and 4.6

34.7 + 41 = 75.7 22.8 + 41 = 63.8 13.9 + 48 = 51.9 ppm

You can Choose Which Base Value from Table 4.5 to Use

OH

OH

34.7 + 41 + (-5) + 3(9.4) + (-2.5) + (-7.2) = 89.2 ppm

C-3 -OH -OH 2o(3o) 2o(4o)

OH

OH

36.9 + 41 + (-5) + 2(9.4) + (-2.5) = 88.8 ppm

C-3 -OH -OH 2o(3o)

Spectrum at 75 MHz and 150 MHz