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OH radical-initiated atmospheric oxidation of ethyl acrylate (ethyl 2-propenoate, EA) has been investigated by performing density functional theory (DFT) calculations. Optimizations of the reactants, intermediates, transition states and products were carried out at the MPWB1K/6-31+G(d,p) level. Single-point energy calculations were performed at the MPWB1K/6-311+G(3df,2p) level of theory. The detailed oxidation mechanism was presented and discussed. The results show that the OH addition is more energetically favorable than the H abstraction. Rice–Ramsperger–Kassel–Marcus (RRKM) theory was used to predict the rate constants over the possible atmospheric temperature range of 180–370 K. The Arrhenius expression adequately describes the total rate constant: k (EA+OH) = (1.71 × 10 −12 )exp(805.42/ T ) cm 3 molecule −1 s −1 . At 298 K, the atmospheric lifetime of ethyl acrylate determined by OH radicals is about 16.2 h. In order to find out the effect of alkyl substitution on the reaction activity, rate constants for the reactions of methyl acrylate, methyl methacrylate and butyl acrylate with OH radicals were also discussed. Calculation results show that the reaction activity may increase with the increased electron-donating substitution for electrophilic addition reaction. [ABSTRACT FROM AUTHOR]

Quantum chemical calculations were carried out to investigate the homogeneous gas-phase formation of mixed polybrominated/chlorinated dibenzo- p -dioxins/benzofurans (PBCDD/Fs) from the cross-condensation of 2-chlorophenoxy radical (2-CPR) with 2-bromophenoxy radical (2-BPR), 2,4-dichlorophenoxy radical (2,4-DCPR) with 2,4-dibromophenoxy radical (2,4-DBPR), and 2,4,6-trichlorophenoxy radical (2,4,6-TCPR) with 2,4,6-tribromophenoxy radical (2,4,6-TBPR). The geometrical parameters and vibrational frequencies were calculated at the MPWB1K/6-31+G(d,p) level, and single-point energy calculations were performed at the MPWB1K/6-311+G(3df,2p) level of theory. The rate constants of the crucial elementary reactions were evaluated by the canonical variational transition-state (CVT) theory with the small curvature tunneling (SCT) correction over a wide temperature range of 600–1200 K. Studies show that the substitution pattern of halogenated phenols not only determines the substitution pattern of the resulting PBCDD/Fs, but also has a significant influence on the formation mechanism of PBCDD/Fs, especially on the coupling of the halogenated phenoxy radicals. [ABSTRACT FROM AUTHOR]

Due to its prevalent presence, it is critical to clarify the atmospheric fate of acenaphthylene (Ary). In this paper, the reaction mechanism of the gas-phase ozonolysis of Ary was investigated by using quantum chemistry methods. Possible reaction pathways were discussed, and the theoretical results were compared with the available experimental data. The rate constants of the crucial elementary reactions were determined by the Rice–Ramsperger–Kassel–Marcus (RRKM) theory. The main products include secondary ozonide, naphthalene-1,8-dicarbaldehyde, 1,8-naphthalic anhydride, oxaacenaphthylene-2-one, 1-naphthaldehyde, 2-hydroxy-1-naphthaldehyde, and α-hydroxyhydroperoxide. The reaction of the unsaturated cyclo-pentafused ring with O3 is the dominant pathway. The overall rate constant of the O 3 addition reaction is 5.31 × 10 − 16 cm 3 molecule − 1 s − 1 at 298 K and 1 atm. The atmospheric lifetime of Ary determined by O 3 is about 0.75 h. This work provides a comprehensive investigation of the ozonolysis of Ary and should help to understand its atmospheric fate. [ABSTRACT FROM AUTHOR]

Chlorinated polycyclic aromatic hydrocarbons (ClPAHs) have become a serious environmental concern due to their widespread occurrence and dioxin-like toxicities. In this work, the mechanism of the OH-initiated atmospheric oxidation degradation of 9,10-dichlorophenanthrene (9,10-Cl 2 Phe) was investigated by using high-accuracy quantum chemistry calculations. The rate constants of the crucial elementary reactions were determined by the Rice–Ramsperger–Kassel–Marcus (RRKM) theory. The theoretical results were compared with the available experimental data. The main oxidation products are a group of ring-retaining and ring-opening compounds including chlorophenanthrols, 9,10-dichlorophenanthrene-3,4-dione, dialdehydes, chlorophenanthrenequinones, nitro-9,10-Cl 2 Phe and epoxides et al. The overall rate constant of the OH addition reaction is 2.35 × 10 − 12 cm 3 molecule − 1 s − 1 at 298 K and 1 atm. The atmospheric lifetime of 9,10-Cl 2 Phe determined by OH radicals is about 5.05 days. This study provides a comprehensive investigation of the OH-initiated oxidation degradation of 9,10-Cl 2 Phe and should contribute to clarifying its atmospheric fate. [ABSTRACT FROM AUTHOR]

Highlights: [•] Quantum chemical methods are employed to study the title reactions. [•] Major products of the title reactions are indicated in this study. [•] The rate constant of title reaction is calculated in the first time. [•] The lifetime of DMP is also determined. [ABSTRACT FROM AUTHOR]

Highlights: [•] Gas-phase formation of PBDD/Fs from 2,4,5-TBP and 3,4-DBP was studied by DFT. [•] Only BPs with bromine at the ortho position are capable of forming PBDDs. [•] The formation of PBDDs dominates over the formation of PBDFs. [•] The meta bromine facilitates the dimerization of BP radicals, whereas the para and ortho ones suppress it. [•] The formation of PBDDs from BPs is easier compared to that of the analogous PCDDs from CPs. [Copyright &y& Elsevier]

Abstract: Trichlorfon [O,O-dimethyl-(2,2,2-trichloro-1-hydroxy-ethyl) phosphonate] (TCF) is a kind of widely used organophosphorus pesticides. In this paper, the mechanism and possible oxidation products for the OH-initiated reactions of TCF are studied at the MPWB1K/6–311+G(3df,2p)//MPWB1K/6–31+G(d,p) level. The study shows that H abstraction reaction from the CH3 group and the CH group as well as OH addition reaction to the P atom are energetically favorable for the reactions of TCF and the main products are (CH3O)2POOH (P1), CCl3CHOHPOOH(OCH3) (P2), CH3OPO2 (P3), CCl3COPO(OCH3)2 (P6) and HCHO. On the basis of the quantum chemical information, the kinetic calculation is performed and the rate constants are calculated over a temperature range of 200–800K using the transition state theory and canonical variational transition state theory with small-curvature tunneling effect. The Arrhenius formulas of rate constants with the temperature are fitted and the lifetimes of the reaction species in the troposphere are estimated according to the rate constants, which can provide helpful information for the model simulation study. [Copyright &y& Elsevier]

Abstract: The ocimene ozonolysis reaction is one of the most important processes for the formation of secondary organic aerosol (SOA). In this paper, molecular orbital theory has been performed for the reaction of ocimene with O3, and the detailed reaction mechanisms of active intermediates with H2O or NO are also presented. The geometry parameters and vibrational frequencies of the stationary points are calculated at the MPWB1K level with the 6-31G(d,p) basis set. Single-point energy calculations are carried out at the MPWB1K/6-311+G(3df,2p) level. On the basis of the quantum chemical information, the Rice–Ramsperger–Kassel–Marcus (RRKM) theory and the canonical variational transition state theory (CVT) with small-curvature tunneling effect (SCT) are used to calculate the rate constants over the temperature range of 200–800 K. The arrhenius formulas of rate constants with the temperature are fitted, which can provide helpful information for the model simulation study. The atmospheric lifetimes of the reaction species are estimated according to the rate constants. [Copyright &y& Elsevier]