What are aromatic hydrocarbons?

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Answer 1 · 2015-05-07T22:35:48

An aromatic hydrocarbon is a hydrocarbon that contains #4n+2# electrons in a planar conjugated π system (#n = 0, 1, 2, …#).

The most common aromatic compounds contain benzene rings (#n = 1#).

preparatorychemistry.com

Examples are toluene and trinitrotoluene (TNT).

hyperphysics.phy-astr.gsu.edu

But any planar cyclic hydrocarbon that contains 2, 6, 10, 14 … π electrons is aromatic.

Examples are naphthalene (10 π electrons) and phenanthrene (14 π electrons).

The ring doesn't have to contain a 6-membered ring, as long as it is planar contains #4n+2# π electrons

Thus, [18]annulene is aromatic. It is planar and possesses #4n+2# π electrons (with #n = 4#).

www.chem.unc.edu