Oxidative transformations of 1-nitropyrene under simulated environmental conditions

Area of Science:

• Environmental Chemistry
• Organic Chemistry
• Atmospheric Chemistry

Background:

• 1-Nitropyrene (1-NP) is a polycyclic aromatic hydrocarbon derivative.
• Oxidation reactions are crucial in atmospheric chemistry and pollutant transformation.
• Dimethyldioxirane (DMD) is a potent epoxidizing agent.

Purpose of the Study:

• To investigate the oxidation products of 1-nitropyrene (1-NP).
• To compare the oxidation efficacy of dimethyldioxirane (DMD) and products from tetramethylethylene (TME)/ozone reactions.
• To identify the reactive oxidant species in the TME/ozone system.

Main Methods:

• Adsorption of 1-NP on silica gel.
• Oxidation of adsorbed 1-NP using DMD.
• Exposure of adsorbed 1-NP to gas-phase TME/ozone reaction products at -40°C.
• Analysis of 1-nitropyrene oxide formation ratios.

Main Results:

• DMD oxidation of 1-NP yielded 1-nitropyrene 4,5-oxide and 1-nitropyrene 9,10-oxide in a 74/26 ratio.
• TME/ozone reaction products oxidized 1-NP to the same oxides in a 72/28 ratio.
• Ozone alone did not produce oxides, indicating a different oxidant was involved in the TME/ozone experiment.

Conclusions:

• The similar oxide ratios suggest DMD is the primary oxidant in both experimental setups.
• The TME/ozone reaction likely produces DMD in situ, possibly via an acetone oxide intermediate.
• DMD is proposed as the key oxidant responsible for 1-NP epoxidation in the TME/ozone system.