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Wize University Chemistry Textbook > Structure Elucidation (IR Spectroscopy, NMR, Mass Spectrometry)

Summary

UV-Vis, Fluorescence, and PhosphorescencePrevious Section
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Spectroscopy Overview


1) Determine molecular weight from mass spectrum
  • get this from looking for the M+ fragment (has the heaviest mass)

2) Determine # of unique Hs from H1-NMR spectrum
  • get this for the overall # of peaks

3) Determine the # of unique Cs from the C13-NMR spectrum (if it shows splitting as well you will be able to see how many Hs are attached to each of those Cs
  • overall # of peaks=# of unique Cs
  • if there is coupling, for a unique C, the # of small peaks for that C -1=the number of Hs directly bound to those Cs

4) Examine each spectrum for obvious elements:
  • Examine IR spectrum for presence or absence of carbonyl groups (C=O), hydroxyl groups, NH groups, etc
  • shows functional groups
  • examine mass spectrum for typical fragments like ArCH3- (where Ar=aromatic/benzene ring), CH3CO-, CH3-, etc
  • examine UV-VIS spectrum for evidence of conjugation, aromatic rings, etc
Extra Practice
NMR Spectroscopy: Structure Elucidation 2
Below are the experimental IR, 1H and 13C NMR spectra of an unknown C11-organic compound. The molecular formula of the compound is: C11H14O2 What is the structure of the compound?
MS peaks: 163 (100), 178 (21.0)
NMR Spectra: Structure Elucidation
Below are the experimental 1H and 13C NMR spectra of an unknown organic compound, and IR data is given. The molecular formula of the molecule is: C7H14O. What is the structure of the compound?
IR peaks: 2974 cm-1 and 1716 cm-1
NMR Spectra: Structure Elucidation
Below are the experimental 1H and 13C NMR spectra of an unknown organic compound, and the MS and IR data is given. What is the structure of the compound? Label relevant spectral data in each spectra you can use to base your assignment on (each spectra must be labelled). The molecular ion is not observed in the MS spectra, so what are the peaks?
MS peaks [molecular ion not observed]: 43 (100), 71 (29); IR peaks: 2974 cm-1 and 1716 cm-1
NMR Spectra: Structure Elucidation
Below are the experimental 1H and 13C NMR spectra of an unknown organic compound, and the MS and IR data is given. What is the structure of the compound? Label relevant spectral data in each spectra you can use to base your assignment on (each spectra must be labelled). The molecular ion is not observed in the MS spectra, so what are the peaks?
MS peaks [molecular ion not observed]: 43 (100), 71 (29); IR peaks: 2974 cm-1 and 1716 cm-1
NMR Spectra: Structure Elucidation
Below are the experimental IR, 1H and 13C NMR spectra of an unknown C11-organic compound, and the important MS data is given. What is the structure of the compound? Label relevant spectral data in each spectra you can use to base your assignment on (each spectra must be labelled).
MS peaks: 163 (100), 178 (21.0)
NMR Spectra: Structure Elucidation
Below are the experimental IR, 1H and 13C NMR spectra of an unknown C11-organic compound, and the important MS data is given. What is the structure of the compound? Label relevant spectral data in each spectra you can use to base your assignment on (each spectra must be labelled).
MS peaks: 163 (100), 178 (21.0)
NMR Spectra: Structure Elucidation
Below are the experimental 1H and 13C NMR spectra of an unknown organic compound, and the MS and IR data is given. What is the structure of the compound? Label relevant spectral data in each spectra you can use to base your assignment on (each spectra must be labelled). The molecular ion is not observed in the MS spectra, so what are the peaks?
MS peaks [molecular ion not observed]: 43 (100), 71 (29); IR peaks: 2974 cm-1 and 1716 cm-1
NMR: Structure Elucidation
Below are the experimental 1H and 13C NMR spectra of an unknown organic compound, and the MS and IR data is given. What is the structure of the compound? Label relevant spectral data in each spectra you can use to base your assignment on (each spectra must be labelled). The molecular ion is not observed in the MS spectra, so what are the peaks?
MS peaks [molecular ion not observed]: 43 (100), 71 (29); IR peaks: 2974 cm-1 and 1716 cm-1
NMR Spectroscopy: Structure Elucidation 2
Below are the experimental IR, 1H and 13C NMR spectra of an unknown C11-organic compound. The molecular formula of the compound is: C11H14O2 What is the structure of the compound?
MS peaks: 163 (100), 178 (21.0)