Explain the following: a.) The cycloheptatrienyl anion is antiaromatic, whereas the cyclononatetraenyl anion is planar (in spite of the angle stain involved) and appears to be aromatic. b.) Although  annulene is not aromatic, it adds two electrons readily to form an aromatic dianion.© BrainMass Inc. brainmass.com September 25, 2018, 9:37 pm ad1c9bdddf - https://brainmass.com/chemistry/organic-chemistry-bonding/aromatic-compounds-cycloheptatrienyl-32613
The cycloheptatrienyl anion has 8Pi electrons as shown via Frost's circle (or the polygon rule). The two non-bonding electrons in this anion would be unhybridized leading to 2 more Pi electrons plus the 6Pi electrons from the 3 double bonds. Huckel's rule of ...
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