PHOTOCHEMICAL DEGRADATION OF 1,6- AND 1,8-DINITROPYRENE IN SOLUTION

The molecular phototransformation mechanism of nitroarenes, genotoxic and ubiquitous pollutants in the atmosphere, is still under debate. With increasing exposure to radiation 1,6- and 1,8-dinitropyrene (DNP) in acetonitrile showed a decrease in their characteristic absorption bands (396 and 411 nm, respectively) in the presence of O ₂ , N ₂ and H ₂ O, and an increase in the 220–390 nm region and above 450 nm, indicating their photodegradation and transformation. The resulting photoproducts were highly fluorescent, presenting a broad emission band around 520–540 nm. Oxygen reactive species did not seem to be produced in the principal photodegradation pathways, since photodegradation rates were similar to those in anaerobic samples. In the presence of O ₂ or N ₂ 1,6-DNP photodegraded 4 times faster than 1,8-DNP, while in the presence of water is 1.5 times faster. Two chromatographic fractions were separated, and identified as pyrenediones using authentic samples and reported spectral data for hydroxy-nitropyrenes. Other chromatographic fractions are still to be identified. The properties of the identified products suggested that these were formed through a nitro-nitrite rearrangement.

Keywords:

• nitroarenes
• 1,6-dinitropyrene
• 1,8-dinitropyrene
• photodegradation

We acknowledge financial support by RISE Program, MBRS-SCoRE Program (S06 GM 08102-29), and NASA Space Grant Fellowship.

Notes

^a Continuous photolysis for one hour

^b Relative yield = (product peak area/photodestroyed DNP area) × 100

^c photodegradation percent of 1,6-DNP.

^a Continuous photolysis for one hour

^b Relative yield = (product peak area/photodestroyed DNP area) × 100

^c photodegradation percent of 1,8-DNP.