Demonstrating a New Valence-Bond Interpretation of Conjugation in Polycyclic Conjugated Hydrocarbons with a Single Kekulé Structure

Abstract

For polyene molecules with a single classical structure, those with more double bonds and more rings have more Dewar resonance structures. The more Dewar resonance structures a polyene has the more it is conjugated and stable. These generalizations are illustrated by comparing sets of molecules with the same number of fixed double bonds. A step-by-step algorithm for rapidly determining the number of Dewar resonance structures in small typical conjugated polyenes is given. Some new analytical equations for the number of Dewar resonance structures (DS) for series of pyrene-related conjugated polyenes with a single classical structure are also presented. Some general qualitative rules for evaluating relative order of conjugation in polyenes are summarized.

Key Words::

• conjugation
• Dewar resonance structures
• polyene hydrocarbons
• resonance-theoretic analysis
• valence-bond