Chapter 14, Problem 28P

Interpretation Introduction

Interpretation:

The aromaticity of cyclononatetraenyl anion and the dianion formed by $\left[16\right]$ annulene is to be explained.

Concept introduction:

In accordance with the Huckel’s rule, aromatic compounds contain a planar ring and have a conjugated pi system with $(4n+2)\pi$ electrons, where $n=0,1,2,3,\mathrm{...}$

Aromatic compounds contain conjugated pi bonds.

All the atoms in the aromatic ring have an unhybridized $p$ orbital.

Compounds that are planar, cyclic and having conjugated pi system, with $(4n)\pi$ electrons are antiaromatic. They are highly unstable.