Chapter 14, Problem 37P

Interpretation Introduction

Interpretation:

The protons of $\text{[24]}$ annulenes that are more shielded is to be predicted.

Concept introduction:

Annulenes have a conjugated electron $\pi$ system, which produces an induced magnetic field.

If the annulene is anti aromatic in nature, then the direction of the induced magnetic field is the same as the direction of applied external magnetic field, and the outer protons are more shielded.

If the annulene is aromatic, then the direction of the induced magnetic field is opposite to the direction of applied external magnetic field, and the inner protons are more shielded.