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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]

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]

Abstract: The bromophenoxy radicals (BPRs) are key intermediate species involved in the formation of polybrominated dibenzo-p-dioxin/dibenzofurans (PBDD/Fs). In this work, the formation of BPRs from the complete series reactions of 19 bromophenol (BP) congeners with H and OH radicals were investigated theoretically by using the density functional theory (DFT) method and the direct dynamics method. The geometries and frequencies of the reactants, transition states, and products were calculated at the MPWB1K/6-31+G(d,p) level, and the energetic parameters were further refined by the MPWB1K/6-311+G(3df,2p) method. The rate constants were evaluated by the canonical variational transition-state (CVT) theory with the small curvature tunneling (SCT) contribution over a wide temperature range of 600–1200K. The present study indicates that the reactivity of the O–H bonds in BPs as well as the formation potential of BPRs from BPs is strongly related to the bromine substitution pattern. The obtained results can be used for future estimates of PBDD/F emissions quantity based on the well estimated PCDD/F inventory. [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: Diazinon is a member of the organophosphorus class of insecticides. It has been regarded as an important atmospheric pollutant because of its high detection-frequency in the air and potential adverse effects on humans and wildlife. In this paper, the reaction mechanism and possible degradation products for the OH-initiated atmospheric degradation of diazinon were investigated and the rate constants of crucial elementary steps over the temperature range of 180–370 K were predicted. Present results show that OH addition to C4 atom in the pyrimidyl ring, H abstraction from the –CH– moiety as well as OH addition to P atom are the dominant pathways for the reaction of diazinon with OH radicals. The dominant degradation products are diazoxon, SO2, P3, CH3CHO, P4, CH3CO, P14 as well as CH3CHCH3. This work provides a comprehensive investigation of the OH-initiated atmospheric degradation of diazinon and should help to clarify its potential risk to non-targets. [Copyright &y& Elsevier]