Question

How do you determine if a compound has an aromatic ring?

Answer 1

Hint: There are few spectroscopic techniques available to find the structure of the compound containing aromatic rings or not. The spectroscopic techniques are proton NMR, carbon NMR, and Infra-red spectroscopy (IR).

Complete answer:
- In the question it is asked how we can find the presence of an aromatic ring in the given compound.
- In IR spectroscopy by using the stretching vibration of the aromatic hydrogens in the functional group region we can identify the presence of the aromatic ring in the structure of the compound.
- The characteristic absorption peaks in IR spectroscopy of the aromatic hydrogens are at 3100 – 3000 due to aromatic C-H stretch, 2000- 1665 combination bands, 1650-1450 strong to medium vibrations of aromatic hydrogens, and 900-675 out of plane C-H bending vibrations.
- In the proton NMR there will be a few peaks from 7 ppm to 9 ppm confirming the presence of aromatic rings.
- In the carbon NMR there will be a few peaks in the region of 125 – 150 ppm confirms the presence of aromatic rings in the structure of the given compound.
- Therefore by using IR, proton NMR and carbon NMR we can find the presence of the aromatic ring in the given compound.

Note: In the field of chemistry IR and NMR spectroscopy have a vast role in the structure elucidation of the organic compounds. These techniques are very useful in the field of research to determine the structures of various compounds.