Interpreting NMR Spectra

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• Interpreting NMR Spectra
• Calculate elements of unsaturation (1/2(2C2-H),
  ignore O,
• halogens count as Hs
• Count number of signals (equals number of types
  of H)
• Check integration to determine ratio of types of
  H
• Check splitting to determine connectivity
• Use chemical shift table to identify types of H
• Work out fragments
• Assemble fragments, remembering rules of bonding
• Check result to make sure it matches formula and
  number
• of types of H.

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C3H8 EoU0
Signal b, 12 units Triplet, 0.91 ppm
2 signals, 2 types of H
Ratio is 13 or 26
a is a septet, so 6 Hs adjacent b is a triplet,
so 2 Hs adjacent
a is at 1.3 ppm CH2? b is at 0.9 ppm CH3?
Structure is CH3CH2CH3
Signal a, 4 Units Septet, 1.34 ppm
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C4H8O2, EoU1
3 signals, 3 types of H
Ratio is 466 (or 233)
a is a quartet, adjacent to 3H b is a singlet,
adjacent to 0H c is a triplet, adjacent to 2H
a at 4.1 ppm, CH2O? b at 2.0 ppm, CH3CO? c at
1.4 ppm, CH3?
Structure is CH3C(O)OCH2CH3
a, quartet 4 units
b, singlet 6 units
c, triplet 6 units
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Mass Spectrometry
Three things happen to molecules inside a mass
spectrometer 1. The molecules are energized in
some way to create ions. 2. The ions are
separated based on their mass/charge ratio. 3.
The ions are detected.
lt 10-6 mm Hg
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Electron Impact Ionizaton

• Generate electrons heated filament
• Accelerate electrons through a potential
  difference (voltage). Commonly electron kinetic
  energy is 80 eV. (conversion 1 eV 96.5 kJ/mole)
• Enough energy to ionize and cause extensive
  fragmentation.

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Magnetic Sector Mass Spectrometer
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Important Isotopes
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Isotopes in MS
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Branched Hydrocarbons

• The MS for branched saturated hydrocarbons are
  similar, except certain fragments become more
  prominent.

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IR Spectrometer

• Lightsource, sample, wavelength selector,
  detector
• CW and FT

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