Computational Studies on the Reactivity of Polycyclic Aromatic Hydrocarbons

Area of Science:

• Environmental Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Polycyclic aromatic hydrocarbons (PAHs) are persistent environmental pollutants with significant toxicity.
• Understanding PAH reaction mechanisms is crucial for environmental risk assessment and remediation strategies.

Purpose of the Study:

• To investigate the reactivity of PAHs in both particle and gas phases using theoretical methods.
• To evaluate the performance of seven quantum chemistry methods, particularly the condensed Fukui function (CFF), for predicting PAH reaction sites and products.
• To elucidate the gas-phase reaction mechanism of fluorene, addressing discrepancies between theoretical predictions and experimental observations.

Main Methods:

• Application of seven quantum chemistry methods to predict reactive sites of 15 PAHs in the particle phase.
• Utilizing the condensed Fukui function (CFF) to identify optimal reactive sites.
• Investigating gas-phase mono-nitration reactions of eight PAHs.
• Employing transition state theory to analyze the reaction mechanism and kinetics of fluorene nitration.

Main Results:

• The condensed Fukui function (CFF) demonstrated optimal performance in predicting reactive sites for PAHs in the particle phase.
• CFF accurately predicted gas-phase mono-nitro products for seven out of eight investigated PAHs.
• For fluorene, CFF initially predicted 1-nitrofluorene and 3-nitrofluorene, inconsistent with experimental data.
• Transition state theory calculations revealed that the formation rates of 3-nitrofluorene and 2-nitrofluorene are significantly higher than 1-nitrofluorene, aligning with experimental findings.

Conclusions:

• The condensed Fukui function (CFF) is a reliable method for predicting PAH reactivity in environmental contexts.
• Theoretical methods, including transition state theory, can effectively explain and predict complex reaction mechanisms of environmental pollutants like fluorene.
• Further investigation into the reaction mechanisms of PAHs is essential for understanding their environmental fate and impact.