title: Influence of water on the homogeneous gas-phase formation mechanism of polyhalogenated dioxins/furans from chlorinated/brominated phenols as precursors.
abstract: Water is of great chemical importance due to its ability to form hydrogen bond. Polyhalogenated dibenzo-p-dioxin/benzofurans (PHDD/Fs) are notorious due to their persistence, bioaccumulation and extremely high toxicity. Water is ubiquitous, and a deep knowledge of its influence on the formation mechanism of PHDD/Fs is necessary. This work investigated the influence of water on the homogeneous gas-phase formation of PHDD/Fs from halogenated phenols (HPs) as precursors by using quantum chemical calculations with the aid of the MPWB1K theoretical approach in connection with the 6-31+G(d,p) and 6-311+G(3df,2p) basis sets. The schematic energy profile in the presence of water was constructed and compared with the situation without water. This study reveals for the first time that the introduction of water promotes the formation of halogenated phenoxy radicals (HPRs) from the H abstraction reactions of HPs with atomic H and OH radicals by lowering the reaction energy barriers and opening new low-energy pathways. Another intriguing finding of this work is that the inclusion of a water molecule produces a catalytic effect on the H-shift step involved in the formation of PHDFs and thus their formation potential is enhanced.
authors.affiliation: Environment Research Institute, Shandong University, Jinan 250100, PR China.
authors.forename: Xiangli
authors.initials: X
authors.lastname: Shi
authors.affiliation: Environment Research Institute, Shandong University, Jinan 250100, PR China.
authors.forename: Ruiming
authors.initials: R
authors.lastname: Zhang
authors.affiliation: Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, PR China.
authors.forename: Haijun
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Environment Research Institute, Shandong University, Jinan 250100, PR China.
authors.forename: Fei
authors.initials: F
authors.lastname: Xu
authors.affiliation: Environment Research Institute, Shandong University, Jinan 250100, PR China. Electronic address: zqz@sdu.edu.cn.
authors.forename: Qingzhu
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Environment Research Institute, Shandong University, Jinan 250100, PR China.
authors.forename: Wenxing
authors.initials: W
authors.lastname: Wang
mesh_terms: D001572:Benzofurans / Q000737:chemistry*; D000072338:Dibenzofurans, Polychlorinated; D004785:Environmental Pollutants / Q000737:chemistry*; D006842:Hydrocarbons, Brominated / Q000737:chemistry*; D007700:Kinetics; D008956:Models, Chemical; D044367:Phase Transition; D010636:Phenols / Q000737:chemistry*; D000072317:Polychlorinated Dibenzodioxins / Q000031:analogs & derivatives* / Q000737:chemistry; D014867:Water / Q000737:chemistry*
chemical_list: D001572:Benzofurans; D000072338:Dibenzofurans, Polychlorinated; D004785:Environmental Pollutants; D006842:Hydrocarbons, Brominated; D010636:Phenols; D000072317:Polychlorinated Dibenzodioxins; D014867:Water; C042329:phenoxy radical
keywords: BPs; CPs; Catalysis; Formation mechanism; Halogenated dioxins/furans; Water molecule