《A new bi-radical species formed during the photochemical degradation of synthetic musk tonalide in water: Study of in-situ laser flash photolysis and validation of synthesized standard sample》

Website： http://dx.doi.org/10.1016/j.scitotenv.2022.160311

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ABSTRACT：

The ubiquitous presence of synthetic musks is causing serious concern due to their transformation species and environmental impacts. In this study, tonalide (AHTN) was selected as a model of synthetic musks to find out the transformation mechanism and pathway in water under UV irradiation. Results showed that AHTN could undergo rapid photochemical degradation via a new pivotal biradical as the initial active species. The biradicals with a typical absorption peak at 340 nm was observed by in-situ laser flash photolysis technology, and the absolute decay rate constant was obtained as 3.61 ± 0.01×10⁹ M^-1s^-1 with the life-time of 83.3 ns. The photochemical degradation by-products of AHTN were also identified by high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry, and the precise structures of key by-products have been validated by our preparative synthesized standard samples confirmed by nuclear magnetic resonance. Thus, the mechanism of AHTN photochemical degradation, continuous photoenolization of the biradicals and followed cycloaddition reaction with O₂, was proposed as the predominant pathway. The main degradation by-product, photoenol which has a higher bioconcentration factors than that of AHTN, were found to form from the biradicals photoenolization. This study is the first work to propose a new biradical as the photoenol precursors during photochemical degradation of AHTN in water.