Aromaticity of azines through dyotropic double hydrogen transfer reaction

Area of Science:

• Computational Chemistry
• Theoretical Chemistry
• Organic Chemistry

Background:

• Aromaticity is a key concept in understanding the stability and reactivity of cyclic compounds.
• Quantifying aromaticity in nitrogen-containing heterocycles like azines presents unique challenges.
• Dyotropic double hydrogen transfer (DDHT) reactions offer a novel pathway to probe molecular properties.

Purpose of the Study:

• To quantify the aromaticity of mono- to triazines using computational methods.
• To investigate the relationship between DDHT reaction energetics and azine aromaticity.
• To compare activation energies and reaction energies as indicators of aromaticity.

Main Methods:

• Density functional theory (DFT) calculations at the B3LYP/6-31+G(d) level.
• Analysis of activation barriers and reaction energies for DDHT reactions.
• Comparison of calculated aromaticity with geometric and magnetic criteria (e.g., NICS(0)πzz).

Main Results:

• Reactions yielding highly aromatic azines exhibited small activation barriers and high reaction energies.
• Activation energies were found to be superior indicators of aromaticity compared to reaction energies.
• Calculated aromaticities for most azines were comparable to that of benzene.
• Thermodynamic contributions from contiguous nitrogen atoms and fusion to the reaction center were identified.

Conclusions:

• DDHT reactions provide a reliable method for assessing azine aromaticity.
• Activation energies in DDHT reactions are effective for quantifying aromaticity, even in complex systems.
• Corrected aromaticity values correlate well with established literature data, validating the approach.