A1 Refereed original research article in a scientific journal
Unveiling chlorine's role: How it shapes the formation and light-activated oxygen dynamics of chlorophenol-derived environmental persistent free radicals
Authors: Jin, Xingzhi; Gao, Di; Zhang, Chunyan; Chen, Chen; Li, Yuyue; Chen, Hao; Cai, Peng; Li, Jianwei; Ding, Xing
Publisher: Elsevier BV
Publishing place: AMSTERDAM
Publication year: 2024
Journal: Journal of Hazardous Materials
Journal name in source: Journal of Hazardous Materials
Journal acronym: J HAZARD MATER
Article number: 135870
Volume: 480
Number of pages: 10
ISSN: 0304-3894
eISSN: 1873-3336
DOI: https://doi.org/10.1016/j.jhazmat.2024.135870
Web address : https://doi.org/10.1016/j.jhazmat.2024.135870
Abstract
Environmental persistent free radicals (EPFRs) derived from chlorophenols, triggered by light or heat exposure, pose significant ecological concerns, yet the impact of chlorine substituents on EPFRs formation and reactivity remains inadequately understood. Through an intentional synthesis of chlorophenol-derived EPFRs with varying chlorine contents and positioning, we elucidated the role of chlorine in the photoactivation of molecular oxygen. Our combined experimental and theoretical analysis reveals that these EPFRs are primarily oxygen-centered phenoxy radicals, establishing a direct link between chlorine substitution patterns and their ability to activate molecular oxygen under visible light. Increased chlorine content enhances EPFRs formation by elevating the positive charge on the phenolic hydroxyl group's hydrogen atom, facilitating its removal. Moreover, the capability of EPFRs to activate molecular oxygen was directly correlated with chlorine content, with 2,3,5,6-tetrachlorophenol-derived EPFRs showcasing the highest activity. This activity is attributed to their structural propensity for TCSQ & sdot;-species & sdot;- species generation. Furthermore, our study established a significant correlation between the toxicity and activity of EPFRs, emphasizing the critical role of halogen substituents in determining the reactivity of EPFRs. These insights contribute to our understanding of their environmental and toxicological ramifications, underscoring the imperative for continued research aimed at mitigating their detrimental impacts.
Environmental persistent free radicals (EPFRs) derived from chlorophenols, triggered by light or heat exposure, pose significant ecological concerns, yet the impact of chlorine substituents on EPFRs formation and reactivity remains inadequately understood. Through an intentional synthesis of chlorophenol-derived EPFRs with varying chlorine contents and positioning, we elucidated the role of chlorine in the photoactivation of molecular oxygen. Our combined experimental and theoretical analysis reveals that these EPFRs are primarily oxygen-centered phenoxy radicals, establishing a direct link between chlorine substitution patterns and their ability to activate molecular oxygen under visible light. Increased chlorine content enhances EPFRs formation by elevating the positive charge on the phenolic hydroxyl group's hydrogen atom, facilitating its removal. Moreover, the capability of EPFRs to activate molecular oxygen was directly correlated with chlorine content, with 2,3,5,6-tetrachlorophenol-derived EPFRs showcasing the highest activity. This activity is attributed to their structural propensity for TCSQ & sdot;-species & sdot;- species generation. Furthermore, our study established a significant correlation between the toxicity and activity of EPFRs, emphasizing the critical role of halogen substituents in determining the reactivity of EPFRs. These insights contribute to our understanding of their environmental and toxicological ramifications, underscoring the imperative for continued research aimed at mitigating their detrimental impacts.
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