Problem #7: The molecular formula for an unknown compound is C8H7N. Data for the 1H NMR, 13C NMR, infrared and mass spectra for this compound are available by clicking on the buttons below; use the "Return" button to return to this screen. Help with the interpretation of each spectrum is available and you can review background and selected correlation tables by clicking on the links in the MENU above. Using the spectral and analytical information provided, determine the structure for this compound.

 





















 

NMR Spectrum
Problem #7: C8H7N

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 Problem #7: C8H7N

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 Problem #7: C8H7N
13C NMR: quartet: 22.0 ppm singlet: 116.5 ppm two singlets: 109.5, 142.0 ppm; two doublets: 129.9, 131.9 ppm

Problem #7: C8H7N

  • The molecule contains a nitrogen, and from the analysis, contains six double bonds or rings. The large number of degrees of unsaturation strongly suggests an aromatic compound (DU = 4).
  • The mass spectrum displays a molecular ion and a small peak which suggests loss of HCN. The data are consistent with a molecule containing a nitrile which does not readily form stable cations.
  • The 13C spectrum contains six peaks, indicating that the molecule has some elements of symmetry. The quartet at d 22 represents a simple CH3, slightly deshielded by an electronegative group. The peaks in the aromatic region strongly suggest 1,4-disubstitution, and there is a peak at 117 which would be consistent with a nitrile carbon.
  • The proton NMR also shows evidence for 1,4-disubstitution on an aromatic ring and an isolated methyl with a chemical shift which is consistent with direct attachment to the ring.
  • The IR is consistent with an aromatic compound containing a nitrile.
  • The simplest structure which is consistent with all of these data would be an aromatic compound with a nitrile and a methyl group, 1,4 to each other on the ring.