Date of Award
Thesis campus only
Studying and synthesizing antiaromatic dianions offers the potential for a more effective understanding of the factors that affect the properties of aromatic compounds, such as delocalization and HOMO-LUMO gaps. Previous attempts to synthesize benzylidene dibenzocycloheptene dianions through reduction with lithium proved to be ineffective because there was over-reduction to an aromatic tetraanion. However, through deprotonation with a strong base, we were able to synthesize an antiaromatic dianion. While invisible on the NMR because of its small HOMO-LUMO gap, an analogue of this compound with a larger HOMO-LUMO gap was synthesized, with the hopes of observing it via NMR spectroscopy. When attempting deprotonation to the antiaromatic dianion, an aromatic trianion was formed instead by subsequent hydride addition, supporting the instability of the antiaromatic dianion. Another focus for this thesis was looking at the effect of phenyl substituents on the delocalization in antiaromatic dianions. Quenching the products demonstrated that the primary intermediates were monoanions from deprotonation and from butyl anion addition, as well as products from hydride loss. There was evidence for the existence of a small amount of antiaromatic dianion, which was converted to a trianion through rapid hydride addition. The NMR spectra of the reaction mixtures of isomeric precursors were consistent with different patterns of delocalization.
Kirkman, Kelsey E., "Antiaromatic Dianions" (2015). Chemistry Student Honors Theses. 2.