Chapter 14, Problem 14.35P

Interpretation Introduction

Interpretation:

The reason for the aromaticity of $\text{pyrene}$ is to be explained.

Concept introduction:

Each $\text{C=C}$ bond consists of two $\text{π}$ electrons. The ${\text{sp}}^{\text{3}}$-hybridized carbon atom isolates one $\text{π}$ system from the other. Two double bonds are part of the same $\text{π}$ system if they are separated by exactly one bond, making the double bonds conjugated. According to Hückel’s rule, if a species possesses a $\text{π}$ system of MOs constructed from p atomic orbital and fully conjugated around a ring, then the species is aromatic if the number of electrons in that cyclic $\text{π}$ system is 2, 6, 10, 14, 18, and so on. (These are called Hückel numbers.) The species is antiaromatic if the number of electrons in that cyclic π system is 4, 8, 12, 16, 20, and so on. (These are called anti-Hückel numbers.)