Formation of chlorobenzenes by oxidative thermal decomposition of 1,3-dichloropropene

Abstract

We combine combustion experiments and density functional theory (DFT) calculations to investigate the formation of chlorobenzenes from oxidative thermal decomposition of 1,3-dichloropropene.Mono-to hexa-chlorobenzenes are observed between 800 and 1150 K, and the extent of chlorination was proportional to the combustion temperature. Higher chlorinated congeners of chlorobenzene (tetra-, penta-, hexa-chlorobenzene) are only observed in trace amounts between 950 and 1050 K.DFT calculations indicate that cyclisation of chlorinated hexatrienes proceeds via open-shell radical pathways. These species represent key components in the formation mechanism of chlorinated polyaromatic hydrocarbons. Results presented herein should provide better understanding of the evolution of soot from combustion/pyrolysis of short chlorinated alkenes.

Formation of benzofuran and chlorobenzofuran from 1,3-dichloropropene: A quantum chemical investigation

“…Intrinsic reaction coordinate pathways were constructed to ensure all transitions states corresponded to the correct reactive pathway. A number of investigations have demonstrated the accuracy of the M06‐2X functional in the context of combustion and related thermochemistry . All reaction and activation enthalpies were then recalculated using the G3MP2B3 composite method .…”

Quantum Chemical Molecular Dynamics Simulations of 1,3-Dichloropropene Combustion

“…G3MP2B3 has been shown to provide accurate reaction and activation enthalpies for the combustion of chlorinated hydrocarbons. 4,34,72 Such a comparison is necessary since the halorg parameters themselves were not explicitly designed for use in the present context. Kinetic parameters of key initiation reactions have also been calculated using G3MP2B3 reaction/activation enthalpies with the CHEMRATE program.…”

“…1−5,16−39 Recent studies suggest that the thermal decomposition of chlorinated straight-chain hydrocarbons proceeds via a unimolecular C−Cl bond scission at the allylic carbon, due to this C−Cl bond being weaker compared to other C−H bonds. 2,4 The primary chemical products (∼90%) of 1,3-D thermolysis are CO, CO 2 , H 2 O, and HCl. 4 HCl formation can occur via H abstraction by Cl from the parent compound and its derived radicals 40−43 or via an intra-annular HCl elimination.…”

“…2,4 The primary chemical products (∼90%) of 1,3-D thermolysis are CO, CO 2 , H 2 O, and HCl. 4 HCl formation can occur via H abstraction by Cl from the parent compound and its derived radicals 40−43 or via an intra-annular HCl elimination. 1,3,30,44−52 However, combustion of non-chlorinated analogous species shows that O 2 abstraction of an allylic H, forming the HO 2 radical, is also an important initiation step.…”

“…73 These parameters have been calculated over a temperature range of 300−3000 K and so are relevant to the simulations that we present in this work and recent experimental investigations. 4 Thermochemical corrections were obtained via the harmonic approximation at 298.15 Chemical reactivity is minimal for the oxidative system at the lowest temperature considered here (1500 K). Indeed, a time scale of 100 ps is insufficient to model the entire combustion process under these conditions.…”