Formation of Chlorotriophenoxy Radicals from Complete Series Reactions of Chlorotriophenols with H and OH Radicals

Abstract

The chlorothiophenoxy radicals (CTPRs) are key intermediate species in the formation of polychlorinated dibenzothiophenes/thianthrenes (PCDT/TAs). In this work, the formation of CTPRs from the complete series reactions of 19 chlorothiophenol (CTP) congeners with H and OH radicals were investigated theoretically by using the density functional theory (DFT) method. The profiles of the potential energy surface were constructed at the MPWB1K/6-311+G(3df,2p)//MPWB1K/6-31+G(d,p) level. The rate constants were evaluated by the canonical variational transition-state (CVT) theory with the small curvature tunneling (SCT) contribution at 600–1200 K. The present study indicates that the structural parameters, thermal data, and rate constants as well as the formation potential of CTPRs from CTPs are strongly dominated by the chlorine substitution at the ortho-position of CTPs. Comparison with the study of formation of chlorophenoxy radicals (CPRs) from chlorophenols (CPs) clearly shows that the thiophenoxyl-hydrogen abstraction from CTPs by H is more efficient than the phenoxyl-hydrogen abstraction from CPs by H, whereas the thiophenoxyl-hydrogen abstraction from CTPs by OH is less impactful than the phenoxyl-hydrogen abstraction from CPs by OH. Reactions of CTPs with H can occur more readily than that of CTPs with OH, which is opposite to the reactivity comparison of CPs with H and OH.

Mechanistic and Kinetic Study on Self-/Cross- Condensation of PCTA/DT Formation Mechanisms from Three Types of Radicals of 2,4-Dichlorothiophenol

“…The reliability and accuracy of the MPWB1K/6-311+G(3df,2p)// MPWB1K/6-31+G(d,p) level for the geometries, frequencies and energy calculation in this study have been confirmed in our previous works on PCTA/DT formation with 2,4-DCTP as the precursor [29,39]. The data was compared with data from Yu and Pan calculated at the BB1K/6-311+G(3df,2p)//BB1K/6-311G(d,p) level [30,36].…”

“…The calculated potential barriers (Δ E ) and the reaction heats (Δ H ) at the MPWB1K/6-311+G(3df,2p)//MPWB1K/6-31+G(d,p) level involved in the formation of R1, R2 and DR radicals from 2,4-DCTP abstracted by the OH, H and Cl are given in the Figure 1a–c. In Figure 1, data of 2,4-DCTP thiophenoxyl-H abstraction by OH and H were cited from our previous studies [39]. All the optimized transition state geometries for 2,4-DCTP abstracted by OH, H and Cl radicals are shown in Figure 2.…”

“…Schematic formation of various radicals from the reactions of 2,4-DCTP with OH ( a ), H ( b ) and Cl ( c ) with the potential barriers Δ E (in kcal/mol) and reaction heats Δ H (in kcal/mol). ( a Reproduced with permission from Xu et al [39]).…”

Mechanistic and Kinetic Studies on the Homogeneous Gas-Phase Formation of PCTA/DTs from 2,4-Dichlorothiophenol and 2,4,6-Trichlorothiophenol

“…The potential barriers (Δ E ) and the reaction heats (Δ H ) of 2,4-DCTP and 2,4,6-TCTP thiophenoxyl-hydrogen cleavage and abstraction by H, OH, O( 3 P), and Cl were calculated at the MPWB1K/6-311+G(3df,2p) level in Table 1 . Data of 2,4-DCTP and 2,4,6-TCTP thiophenoxyl-hydrogen cleavage and abstraction by H and OH were cited from our previous studies [ 39 ]. All the abstraction steps are strongly exothermic.…”

Quantum Chemical and Kinetic Study on Radical/Molecule Formation Mechanism of Pre-Intermediates for PCTA/PT/DT/DFs from 2-Chlorothiophenol and 2-Chlorophenol Precursors

“…The potential barriers (Δ E ) and the reaction heat (Δ H ) which are calculated at the MPWB1K/6-311+G(3df,2p)//MPWB1K/6-31+G(d,p) level for the formation of C(T)PR1, C(T)PR2, C(T)PDR, (T)PR2, and (T)PDR from 2-C(T)P abstracted by the H and OH are given in the Figure 1a,b. In Figure 1, data of sulfydryl/hydroxyl-H abstraction of 2-C(T)P by H and OH are cited from our previous studies at the MPWB1K/6-311+G(3df,2p)//MPWB1K/6-31+G(d,p) level [44,45,46]. Pan et al and Yu et al also studied the formation of C(T)PR1, C(T)PR2, C(T)PDR, (T)PR2, and (T)PDR from 2-C(T)P molecules abstracted by H radical at the BB1K/6-311+G(3df,2p)//BB1K/6-311G(d,p) level [27,41].…”