Chapter 14, Problem 14.23P

Interpretation Introduction

Interpretation:

Assuming the given compound is planar, it is to be determined and explained whether it is aromatic, antiaromatic, or nonaromatic.

Concept introduction:

Electrons can be resonance delocalized over a set of atoms that contribute conjugated p-orbitals to a single $\text{π}$ system of molecular orbitals. For an acyclic conjugated system, the $\text{π}$ electrons are the ones that can be shifted via resonance from one end to the other. Counting of the $\text{π}$ systems and number of electrons is useful when a compound contains a triple bond. According to the MO theory, the two pi bonds are perpendicular to each other in a triple bond. Therefore, only one of those pi bonds can be conjugated with the neighboring $\text{π}$ system.