NMR Chapter 13

1
NMR Chapter 13

• 13C-NMR Spectroscopy
• CHEMISTRY 220
• Spring 2003

2
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

(111)
3
Acetone in Chloroform-d1
Methyl carbons
CDCl3 carbon
Carbonyl carbon
4
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 2nI1 rule.
• DMSO-d6 Acetone-d6, and Methanol-d4 display a
  septet.
• Cyclohexane-d12 displays a pentet.

5
General Chemical Shift Regions
6
2-Butanone (MEK)
a
b
c
This is the form of a typical carbon spectrum
it is proton noise decoupled (see single lines
for all carbons)
Methanol-d6
d
7
Off-Resonance Decoupling (2nI1)
c
a
b
8
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!

9
DEPT from ACDLabs Prediction Software

• In this experiment
• The CH3 and CH carbons are negative
• The CH2 and CH carbons are positive

c
d
b
a
10
Isopropyl
Butanoate
c
b
a
e
f
c
d
b
d
c
e
f
a
11
p-methyl benzoic acid
c
d
a
f
e
b