Mechanism and thermal rate constants for complete series reactions of bromochlorophenols with H

Siyuan Zheng,Xianwei Zhao,Yunfeng Li,Qingzhu Zhang,Fei Xu

doi:10.1039/c7ra12781b

Siyuan Zheng, Xianwei Zhao + Show 3 more

Open Access

https://doi.org/10.1039/c7ra12781b

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Abstract

Formation of bromochlorophenoxy radicals (BCPRs) from the reaction of bromochlorophenols (BCPs) with H can play the most central role in the formation of mixed polybrominated and chlorinated dibenzo-p-dioxins and dibenzofurans (PBCDD/Fs).

Highlights

Mixed polybrominated and chlorinated dibenzo-p-dioxins and dibenzofurans (PBCDD/Fs) are halogenated derivatives of polychlorinated dibenzo-p-dioxin and dibenzofurans (PCDD/Fs) or polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/ Fs), in which all halogen atoms are substituted by both bromine and chlorine atoms
This is consistent with thermodynamic analysis: the different Br and Cl arrangements in BCPs with a given halogen substitution affect the strength of the O–H bonds to a small extent
To be applied more effectively, the canonical variational transitionstate (CVT)/small-curvature tunneling (SCT) rate constants were tted, and Arrhenius formulas are presented in Tables 2 and S4 (ESI†) for Bromochlorophenoxy radicals (BCPRs) formation from the abstraction reactions of the BCPs abstracted by H atom

Summary

Introduction

Mixed polybrominated and chlorinated dibenzo-p-dioxins and dibenzofurans (PBCDD/Fs) are halogenated derivatives of polychlorinated dibenzo-p-dioxin and dibenzofurans (PCDD/Fs) or polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/ Fs), in which all halogen atoms are substituted by both bromine and chlorine atoms. Quantum chemistry calculation and multiple rate constants calculation methods, as a supplement to experimental evaluation, has been successfully employed to elucidate the reaction mechanism and kinetics of organic pollutants in the environment.[32,38,42,43,44,45,50,51] In recent research conducted from this laboratory, we have performed quantum chemistry to investigate the formation of BPRs and CPRs from BPs and CPs with a H atom.[52,53] In the current study, we complemented and expanded on our previous work in this eld to continue mechanistic and kinetic studies into the formation of BCPRs from the reaction of BCPs with H. The results can be input into environmental PBCDD/F control and prediction models as important parameters, which can in turn be used to predict potential PBCDD/F outcomes, con rm PBCDD/F risk analyses, reduce PBCDD/F emissions, and establish PBCDD/F control strategies

Computational method

Results and discussion

Structural analysis

Energy analysis

Rate constant calculation

Conclusion