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

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).

Framework of the Integrated Approach to Formation Mechanisms of Typical Combustion Byproducts─Polyhalogenated Dibenzo-p-dioxins/Dibenzofurans (PXDD/Fs)

“…(a) Potential barriers Δ E (in kcal/mol) for the transformation of chlorophenols (CPs; M = mono, D = di, T = tri, Te = tetra, P = penta) into phenoxy radicals and (b) potential barriers Δ E (in kcal/mol) for the first step of reactions involved in PXDD/Fs formation, i.e., the formation of phenoxy radicals from bromophenols, chlorophenols, and bromochlorophenols. − ,− ,,,− …”

“…The organic free radical intermediates involved in PCDD/Fs formation were recently identified in situ by carrying out electron paramagnetic resonance measurements, making it possible to propose detailed PCDD/Fs formation pathways. , It has been proposed that PCDFs are predominantly formed through radical–radical dimerization involving interactions with metals following the Langmuir–Hinshelwood reactions and PCDDs can form through molecule–radical reactions following the Eley–Rideal reactions. ,, Stable-isotope-labeling techniques have been used to trace the transformation pathways of isotope-labeled precursors to directly identify PCDD/Fs formation mechanisms . Quantum chemical calculations have been used to determine thermodynamic and kinetic parameters for elementary reactions involved in PCDD/Fs formation mechanisms to determine the rationality of the proposed mechanisms and identify energetically favorable reaction pathways. − Thus, PCDD/Fs formation mechanisms can be identified and mutually verified from laboratory studies, theoretical calculations, and field studies.…”