# How do you identify aromatic rings?

Aug 29, 2016

An aromatic ring must be a planar, cyclic, system containing (4n + 2) π electrons in alternating single and double bonds with no intervening saturated carbon atoms.

#### Explanation:

Hückel's rule states that an aromatic system must have ($4 n + 2$) π electrons (#n = 0, 1, 2 ,3, 4, …)

Examples

Thus, benzene is aromatic because it satisfies Hückel's rule.

$4 n + 2 = 6$

$n = 1$

The cyclopropenyl cation is also aromatic.

$4 n + 2 = 2$

$n = 0$

A ring with 4 pi electrons is not aromatic

$4 n + 2 = 4$

$n = \frac{2}{4} = \frac{1}{2}$

n is a fraction.