The isotopological homodesmotic reaction: A further refinement to the quantification of aromaticity

Aromaticity imparts a significant energetic stabilization to various chemical systems as a result of cyclic pi-electron delocalization. One of the most widely used methods for the quantification of the Aromatic Stabilization Energy (ASE) of a molecule is the formulation of a Homodesmotic reaction. The following research employs a refined Homodesmotic approach based on previous work by Herndon and Mills which utilized Isotopological Homodesmotic Reactions (IHR) to determine the Aromatic Stabilization Energy (ASE) of a flourenyl cation. The advantage of employing an IHR for an ASE calculation is that the strain energy contribution from the sigma framework of reactant and product molecules can be strategically canceled-out. An effective Isotopological Homodesmotic Reaction is constructed by using certain cyclic conjugation interrupts in the design of non-aromatic reference structures. Another computational chemistry technique used to probe the aromatic character of the compound in question is the Nucleus Independent Chemical Shift scan (NICS-scan) methodology. The NICS out-of-plane tensor component of a non-chemical probe centered above the molecular plane measures the strength of induced ring currents in a molecule arising from cyclic pi-electron delocalization upon exposure to a magnetic field. The molecules studied range from benzene to buckybowls to fullerenes