Chapter 17, Problem 55IP

Interpretation Introduction

Interpretation: For the given cycloheptatrienone and cyclopentadienone, the more partial negative character on the oxygen atom of cycloheptatrienone should be explained.

Concept introduction:

• A five membered ring will be aromatic if it contains six $\text{π}$ electrons. In order to have six $\text{π}$ electrons, one of the carbon atoms must possess two electrons. It should be a carbanion.
• A seven membered ring will be aromatic if it contains six $\text{π}$ electrons. In order to have six $\text{π}$ electrons in a seven membered ring one of the carbon atom must possess an empty p orbital. This carbocation exhibits a continuous system of overlapping and p orbitals and has six $\text{π}$ electrons.
• Aromatic compounds are more stable than non-aromatic compound
• Cycloheptatrienone reveals resonance structures with aromatic character
• Cyclopentadienone reveals resonance structures with  anti-aromatic character