What is Aromatic Hydrocarbon?
Aromatic hydrocarbons are of course hydrocarbons (that is, made of Hydrogen and Carbon) that have the property of being aromatic. What is aromatic? If a molecule is aromatic we automatically know some things about its electronic structure and stability. Aromatic structures are much more stable than non-aromatic structures do to their delocalized electrons. Each sp2 hybridized Carbon will contain an additional p orbital that extends below the plane of the molecule and above the plane of the molecule. The electrons that populate these p-orbitals are free to move around in all the non-hybridized p-orbitals on each carbon. This makes for the extra stability. Now, how do we know when something is aromatic? We can use Huckel’s rule. Huckel’s rule states that a molecule that has 4n+2 (where n is an integer) electrons in the delocalized p-orbital cloud (like we just discussed). So really you can just count the pi electrons and if it is in accordance with Huckel’s rule (simply you will need 6,1
