Kekulè's Monkey in Anthracene

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This Demonstration shows the four principal resonance structures of anthracene. To better understand how these structures are formed, they can be visualized as a sequence of rotations of the double bonds. As a double bond shared between two rings belongs to both, four different structures can be formed by rotating a shared double bond. Individual resonance structures are actually an abstraction, but these help us to understand the behavior of the molecule.
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Contributed by: D. Meliga, L. Lavagnino and S. Z. Lavagnino (February 2020)
Additional contribution by: S. Borgna
Open content licensed under CC BY-NC-SA
Snapshots
Details
Snapshot 1: first resonance structure of the anthracene; a rotation of the double bond gives the second resonance structure
Snapshot 2: the C-C bond 10a-8a has a bond order of 1.25 as it is a single bond in three separate structures, while in the second one it is a double bond
Snapshot 3: the C-C bond 8-7 has a bond order of 1.75 as it is a double bond in three separate structures, while in the first one it is a double bond
Reference
[1] Wikipedia. "Aromaticity." (Feb 12, 2020) en.wikipedia.org/wiki/Aromaticity.
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