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  • Title: Theoretical and Kinetic Properties of OH Radical-Initiated Oxidation of Galaxolide in the Atmosphere.
    Author: Li Y, Sun Y, Zhang Q.
    Journal: J Phys Chem A; 2018 Nov 29; 122(47):9151-9159. PubMed ID: 30376334.
    Abstract:
    Galaxolide (HHCB), an important emerging contaminant, has attracted great environmental concern owing to its widespread occurrence and potential toxicity. In this study, the detailed multichannel mechanism of OH radical-initiated atmospheric degradation reactions of HHCB has been investigated by employing density functional theory (DFT). The reactants, transition states, intermediates, and products were optimized at the MPWB1K/6-31+G(d,p) level, and single-point energies were further refined at the MPWB1K/6-311+G(3df,2p) level of theory. The canonical variational transition-state (CVT) theory combined with the small curvature tunneling (SCT) was performed to evaluate the Arrhenius expressions and rate constants of key elementary reactions over a suitable range of 180-370 K. The thermodynamic and kinetic calculation results show that OH addition and hydrogen abstraction reactions are competitive pathways for HHCB. The dominant products in the presence of O2/NO are epoxide, dialdehyde, alcohol ketone, cyclolactone compounds, and HO2 radicals. At 298 K, the total rate constant of OH-initiated degradation of HHCB is 2.71 × 10-11 cm3 molecule-1 s-1. The atmospheric lifetime of HHCB determined by OH-initiated reactions is 10.09 h, which is in favor of the phenomenon of medium-range transport for HHCB in the atmosphere.
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