Update for Isomerization Stabilization Energies: The Fulvenization Approach.

Area of Science:

• Computational Chemistry
• Theoretical Chemistry
• Quantum Chemistry

Background:

• Aromatic stabilization energy (ASE) is crucial for understanding chemical stability.
• Existing methods for ASE calculation can be complex or limited in scope.

Purpose of the Study:

• To introduce and validate a novel method for calculating ASE.
• To demonstrate the applicability of the fulvenization approach across diverse molecular systems.

Main Methods:

• Transforming aromatic and antiaromatic rings into their corresponding fulvene isomers.
• Utilizing gas-phase formation enthalpies of parent molecules and fulvene isomers for calculations.
• Applying the method to benzene, six-membered rings, polycyclic aromatic hydrocarbons (PAHs), and nonbenzenoid rings.

Main Results:

• Fulvenization yielded ASE values of 34.05 kcal·mol⁻¹ (singlet) and -17.85 kcal·mol⁻¹ (triplet) for benzene.
• Experimental data for benzene and fulvene formation enthalpies provided a comparable ASE of 33.72 kcal·mol⁻¹.
• The method successfully evaluated aromaticity in substituted rings, biradicals, azines, inorganic analogues, and PAHs, aligning with literature findings.

Conclusions:

• The fulvenization approach is an effective and efficient method for calculating ASE.
• This technique can serve as a valuable alternative or complement to existing aromaticity assessment tools.
• The method shows promise for differentiating aromaticity in various ring systems, including PAHs and nonbenzenoid structures.