Small Antiaromatic Rings


  • From a Plenary lecture given at the International Symposium on the Chemistry of Small Rings (Louvain, Belgium, 12–15 September 1967).


According to quantum mechanical calculations, systems with 4n π electrons ought to have anti-aromatic character, i.e. be destabilized by resonance. This prediction is examined for the case of cyclopropenyl anion, the simplest system having 4n π electrons (n = 1). Isolation of compounds containing the cyclopropenyl anion has not, as yet, been achieved; however, kinetic measurements indicate the existence of the ion and confirm the unusual properties predicted.