Chapter 14, Problem 14.12YT

Interpretation Introduction

Interpretation:

Resonance structures of guanine and adenine showing movement of 10 electrons in a single aromatic $\text{π}$ system and resonance structures of cytosine and thymine showing movement of 6 electrons in a single aromatic $\text{π}$ system are to be drawn.

Concept introduction:

Aromaticity can exist in ions as well as neutral molecules. An aromatic species may be overall neutral with atoms having formal charges, or it may also be a charged species. As long as the species follows Huckel’s rules, it will show aromatic stabilization.

This can be determined on the basis of the Lewis structures of the species. The species must have a set of conjugated p orbitals that contribute to a single $\text{π}$ system. It must have a Huckel number of $\text{π}$ electrons that can be shifted once around the ring.