Photochemical reactions between 1,4-benzoquinone and O2•−
2020
The superoxide anion radical (O₂•⁻) is one of the most predominant reactive oxygen species (ROS), which is also involved in diverse chemical and biological processes. In this study, O₂•⁻ was generated by irradiating riboflavin in an O₂-saturated solution using an ultraviolet lamp (λₑₘ = 365 nm) as the light source. The photochemical reduction of 1,4-benzoquinone (p-BQ) by O₂•⁻ was explored by 355-nm laser flash photolysis (LFP) and 365-nm UV light steady irradiation. The results showed that the photodecomposition efficiency of p-BQ was influenced by the riboflavin concentration, p-BQ initial concentration, and pH values. The superoxide anion radical originating from riboflavin photolysis served as a reductant to react with p-BQ, forming reduced BQ radicals (BQ•⁻) with a second-order rate constant of 1.1 × 10⁹ L mol⁻¹ s⁻¹. The main product of the photochemical reaction between p-BQ and O₂•⁻ was hydroquinone (H₂Q). The present work suggests that the reaction with O₂•⁻ is a potential transformation pathway of 1, 4-benzoquinone in atmospheric aqueous environments.
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