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Problem #9: The molecular formula for an unknown compound is C9H10. 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.

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NMR Spectrum
Problem #9: C9H10

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 Problem #9: C9H10

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 Problem #9: C9H10 



























 


13C NMR:

triplet: 44.9 ppm

triplet: 115.1 ppm; doublet:  137.3 ppm

singlet: 140.2; three doublets:  125.7, 128.4, 127.9 ppm









     Problem #9:  C9H10

 
     


     































 





     




    

  • The molecule contains no heteroatoms, and from the analysis, contains five 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, an m-1 peak and a base peak corresponding to a benzyl unit.

  • The 13C spectrum contains seven peaks, indicating that the molecule has some elements of symmetry.  The triplet at d 45 represents a CH2, flanked by electronegative groups.  The peaks in the aromatic region strongly suggest monosubstitution, and there is a doublet and triplet at d137 and 115 which would be consistent with a terminal alkene.

  • The IR shows sharp peaks for unsaturated (sp2) CH and peaks consistent with double bond stretching.

  • The simplest structure which is consistent with all of these data would be a monosubstituted aromatic compound attached to a side-chain bearing a terminal alkene.











©1997 Brooks/Cole Publishing Company