What aromatic compounds follow Hückel's rule?

Answer 1

All aromatic compounds follow Hückel's rule.

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)

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Answer 2

Wyatt Adkins

Aromatic compounds that follow Hückel's rule must have a planar, cyclic structure with a continuous π-electron system containing 4n + 2 π-electrons, where n is a non-negative integer. Examples include benzene, pyridine, and furan.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.