# Difference between any arene and an aromatic compound?

I can't seem to find what the difference between these two is. In my text book, it says that 'arenes are aromatic hydrocarbons containing one or more benzene rings' which to me suggests that arenes are a subgroup of aromatic hydrocarbons and aromatic hydrocarbons need not contain one or more benzene rings. However later on in my book it says that 'any compound with the benzene ring is classified as an aromatic compound', which to me is the exact same definition as that given for an arene. Is there a difference between arenes and aromatic compounds?

• There are non-hydrocarbon compounds (heterocycles) that are aromatic, such as pyridine, pyrrole and furan. It would not be correct to refer to these as arenes. Azulene (an aromatic hydrocarbon with a 5-membered and 7-membered ring) is a grey area for me. – Level River St Nov 8 '14 at 16:18
• Thanks! I think I get it- arenes are a subgroup of aromatic compounds which have a benzene ring. Aromatic compounds need not necessarily have a benzene ring – Meep Nov 10 '14 at 11:56

Arene — Compound which contains a benzene ring

Aromatic Compounds — Compounds having aroma (wait, the modern definition is different, I know)

Every arene is an aromatic compound but every aromatic compound need not be an arene.

Mathematically,

$$\text{arene} \subset \text{aromatic compounds}$$

therefore anything which contains a benzene ring has to be aromatic

Some examples of arenes:

Getting into aromatic compounds, the modern criteria for aromaticity are:

• The molecule is cyclic (a ring of atoms)
• The molecule is planar (all atoms in the molecule lie in the same plane)
• The molecule is fully conjugated (p orbitals at every atom in the ring)
• The molecule has $4n+2$ π electrons ($n=0$ or any positive integer)*

Examples (non-benzenoids):

Now, benzenoids (compounds which contain benzene) do match with this. Therefore, benzene derivatives are aromatic compounds.