Hückel's rule

Benzene, the most widely recognized aromatic compound with six delocalized π electrons (4n + 2, for n = 1).

In organic chemistry, Hückel's rule is a rule that help to determine if a molecule has the properties of an aromatic compound. It is named after chemist Erich Hückel, who formulated it in 1931. A well known compound that fulfills the rule is Benzene.

It states that: A compound to be aromatic, it must contain 4n+2 π delocalized electrons above or below the plane of the molecule and the molecule is supposed to be cyclic or planar.

Example:

It has 3 π bonds.
i.e. 6 π electrons.
According to this rule,

  • 4n+2 π e- = 6 π e-

4n+2 = 6 4n=4
∴ n = 1 which belong to Z(0,1,2,...)

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