2
$\begingroup$

I wish to know why aromatic hydrocarbons like benzene are called aromatic when they can be just called circular to avoid the confusion?

$\endgroup$
  • 1
    $\begingroup$ Molecules must be more than circular to be considered aromatic. $\endgroup$ – canadianer Jan 10 '15 at 4:13
  • $\begingroup$ The ones which smell good are called aromatic I guess. $\endgroup$ – Yashbhatt Jan 10 '15 at 17:52
  • $\begingroup$ Aromatic compounds are more stable due to the resonance in a single plane. I guess they have a very important meaning and can't just be called off circular. Only particular cyclo compounds are aromatic not all. And on top of that, we have other things like anti-aromaticity. I guess the word aromatic has a different and unique meaning for itself. $\endgroup$ – dr.drizzy Feb 26 '18 at 13:31
6
$\begingroup$

Aromaticity is a electronic property of a molecule, not a description of its shape. An aromatic molecule contains a circular system of conjugated π bonds and p orbitals that contains 4n+2 electrons, where n is an integer.

Benzene is aromatic: it has 6 electrons in a circular conjugated system (4n+2=6, n=1).

Cyclooctatetraene is not aromatic: it appears to have a circular conjugated system, but it contains 8 electrons (4n+2=8 would require n=3/2). This molecule actually adopts a non-planar geometry to avoid antiaromaticity.

Cyclohexane is not aromatic, even though it is circular: it does not have a conjugated electron system.

$\endgroup$
2
$\begingroup$

As @Kyle said aromaticity is an electronic property, not a description of shape and so circular would not be an appropriate description, particularly seeing as these molecules are not at all circular (benzene is hexagonal, for example).

The name 'aromatic' is a historical quirk. Supposedly it was used because many of the chemically aromatic substances know at the time happened to have notable aromas although wikipedia seems to dispute this. Several other reputable sites like this and this do support this view though so I'm not sure what the right answer is (or even if anybody knows).

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.