# Why is benzene an aromatic hydrocarbon?

Feb 9, 2015

Benzene is an aromatic hydrocarbon because it obeys Hückel's rule.

Originally, benzene was considered aromatic because of its smell: it has an "aromatic" odor.

It is now considered aromatic because it obeys Hückel's rule:

$4 n + 2$ = number of π electrons in the hydrocarbon, where $n$ must be an integer.

In the case of benzene, we have 3 π bonds (6 electrons), so $4 n + 2 = 6$.

$n = 1$ (an integer). So, benzene is aromatic.

Another example is naphthalene, with two fused benzene rings.

It has 5 π bonds and 10 electrons.

$4 n + 2 = 10$. So, $n = 2$ (an integer).

So, naphthalene is aromatic…