NMR Chapter 13

13C-NMR Spectroscopy

CHEMISTRY 220

Spring 2003

Deuterated Solvents

Deuterium (2H) has a spin quantum No. of 1.

No. of spin states = 2I + 1 = 3 Deuterium does couple to 13C nuclei.

Chloroform-d1:Cl

C D

Cl

Cl Appears as a triplet

(1:1:1)

Acetone in Chloroform-d1

200 150 100 50

30.61

76.2877.08

77.88

206.28

80 75

76.2877.0877.88

O

CH3H3C

Methyl carbons

Carbonyl carbon

CDCl3 carbon

Deuterated Solvents

Deuterium (2H) has a spin quantum No. of 1. Does not couple to protons (1H) for reasons

that are beyond the scope of this course. Multiplicity follows 2nI+1 rule.

DMSO-d6 Acetone-d6, and Methanol-d4 display a septet.

Cyclohexane-d12 displays a pentet.

General Chemical Shift Regions

2-Butanone (MEK)

210 200 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 0

7.7628.9836.57

47.13

47.67

48.21

48.75

49.29

49.83

50.37

209.74

ab

cd

O

abc

d

Methanol-d6

This is the form of a typical carbon spectrum – it is proton noise decoupled (see single lines for all carbons)

Off-Resonance Decoupling (2nI+1)

230 220 210 200 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 0 -10

7.16

7.567.96

8.3628.38

29.18

29.58

36.57

47.67

48.21

48.75

49.29

49.83

50.37

209.74

35 30 25 20 15 10 5

7.16

7.567.96

8.3628.38

28.7829.18

29.5836.17

36.57

36.97

ab

cd

O

abc

DEPT Experiment

Distortioless Enhancement by Polarization Transfer Distinguishes 1o, 2o, 3o, 4o carbons!

Several different types of DEPT experiments Page 488-9 of your text shows two kinds The ACDLabs® Software that you will use in lab

has a different kind – this is the one that I want you to learn!

DEPT from ACDLabs® Prediction Software

230 220 210 200 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 0 -10

7.7628.98

36.57

209.74

ab

cd

O

In this experiment: The CH3 and

CH carbons are negative

The CH2 and CH carbons are positive

a

d

c

b

Isopropyl Butanoate

a

b

c

O

O

a

bc

c

efd

d

ef

75 70 65 60 55 50 45 40 35 30 25 20 15 10 5

13.7818.53

21.84

36.7067.76

75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0

75 70 65 60 55 50 45 40 35 30 25 20 15 10 5

150 100

170 160 150 140 130 120 110 100

172.70

170 160 150 140 130 120 110 100

170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20

21.40

128.90

129.40129.70

143.30167.80

130 129

130 129

p-methyl benzoic acid

a

b

cd

fe

f

e

O OH

CH3a

b

c

d H

HH

H

c

d