Question

What aromatic compounds follow Hückel's rule?

Answer 1

All aromatic compounds follow Hückel's rule.

Explanation:

Hückel's rule states that a planar, cyclic, conjugated molecule is aromatic if it contains 4`n` + 2 π electrons, where `n` = 0 or any positive integer.

See Can I determine aromaticity by Hückel's rule?

Compounds with `n` = 1

The most common examples have `n` = 1. These include

a. Benzene and its derivatives

b. Six-membered heterocyclics like pyridine and pyrimidine

c. Five membered heterocyclics like pyrrole, furan, and thiophene

d. Five-membered anions like cyclopentadienide ion

e. Seven-membered cations like tropylium ion

Compounds with `n` = 0

cyclopropenyl cation

Compounds with `n` = 2

These include naphthalene and azulene.

Compounds with `n ≥ = 3`

These include the annulenes.

[14]-annulene (`n` = 3)

[18]-annulene (`n` = 4)