Oxepin Derivatives Formation from Gas-Phase Catechol Ozonolysis

Area of Science:

• Atmospheric Chemistry
• Quantum Chemistry
• Organic Chemistry

Background:

• Ozonolysis of organic compounds is a key atmospheric process.
• Catechol is a significant atmospheric pollutant.
• Understanding reaction pathways is crucial for atmospheric modeling.

Purpose of the Study:

• To investigate all potential pathways for primary ozonide (POZ) formation during the gas-phase ozonolysis of catechol.
• To elucidate the mechanisms leading to Criegee Intermediates and other products.
• To identify novel reaction routes and their energetic properties.

Main Methods:

• Quantum chemical calculations were employed to map reaction pathways.
• Canonical transition state theory was used to compute rate coefficients for individual reaction steps.
• Calculated rate coefficients were compared with experimental data for validation.

Main Results:

• Calculated rate coefficients for ozone cycloaddition to catechol align well with experimental findings.
• A novel pathway involving *endo*-addition of ozone to the CH═C(OH) bond was identified, leading to oxepin derivatives.
• Oxepin derivatives were found to be energetically competitive with Criegee Intermediates and peroxy acids.

Conclusions:

• The study confirms known POZ formation pathways and identifies a new route through oxepin derivatives.
• The energetic landscape of catechol ozonolysis is more complex than previously understood.
• These findings contribute to a more accurate understanding of atmospheric oxidation mechanisms.