Nuclear Magnetic Resonance Spectroscopy

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Nuclear Magnetic Resonance Spectroscopy
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Learning Objectives
Use high resolution n.m.r spectrum of simple
molecules (carbon, hydrogen oxygen) to
predict The different types of proton present The
relative numbers of each type of proton The
number of protons adjacent to a given
proton Possible structures Given a simple
molecule predict features of the n.m.r spectrum.
Describe the use of D2O to identify OH groups
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Nuclear Magnetic Resonance Spectroscopy
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Nuclear Magnetic Resonance Spectroscopy
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Nuclear Magnetic Resonance Spectroscopy
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H
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Nuclear Magnetic Resonance Spectroscopy
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Nuclear Magnetic Resonance Spectroscopy
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Nuclear Magnetic Resonance Spectroscopy
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Nuclear Magnetic Resonance Spectroscopy
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Absorption peak corresponds to the radio
frequency absorbed
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• Only nuclei with an odd number of nucleons
  (neutrons and protons) possess a magnetic spin
• 1H (proton nmr)
• 13C

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• The vast majority of proton NMR spectroscopy is
  performed on liquids.
• You have a solid sample, what do you dissolve it
  in?

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structure
spectrum
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Proton NMR Spectra
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Electrons around the nucleus shield it from the
applied magnetic field. Different
radio-frequencies are aborbed depending on the
environment of the proton. CHEMICAL SHIFT is a
measure of the magnetic field experienced by
protons in different environments. CHEMICAL SHIFT
is measured in ppm relative to TMS,
Si(CH3)4 CHEMICAL SHIFT tells us about the types
of protons present
A B S O R T I O N
CHEMICAL SHIFT
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A B S O R T I O N
ABSORPTIONS The area under each peak is directly
proportional to the number of protons responsible
for the absorption These areas are most often
presented as integration traces on the spectrum
CHEMICAL SHIFT
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Your Turn
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Our Turn
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Different types of proton? Relative numbers of
each type of proton?
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CH3CH2OH
CH3CH2OH
CH3CH2OH
CH3CH2OH
CHEMICAL SHIFT ppm Type of proton Number of protons
1.0 R-CH3 3
3.5 O-CH2-R 2
4.9 R-O-H 1
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Predict 3 different types of proton Number
protons is in ratio 123 Assign possible types
of proton to chemical shifts obtained
structure
CH3CH2OH
Expect 3 different types of proton Expect peaks
in the following ranges 0.7-1.6ppm
(CH3) 3.3-4.3ppm (CH2-O) 3.5-5.5ppm (OH) Expect
integration 321
spectrum
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Learning Objectives
Use high resolution n.m.r spectrum of simple
molecules (carbon, hydrogen oxygen) to
predict The different types of proton present The
relative numbers of each type of proton The
number of protons adjacent to a given
proton Possible structures Given a simple
molecule predict features of the n.m.r spectrum.
Describe the use of D2O to identify OH groups
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• The number of absorption peaks tells us the
  number of different types of protons.
• The chemical shift helps us identify the type of
  proton.
• The integration values tells us the relative
  number of protons.

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Old Exam Questions
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