Atmospheric Chemistry of Pentafluorophenol: Kinetics and Mechanism of the Reactions of Cl Atoms and OH Radicals

Fourier transform infrared smog chamber techniques were used to study the kinetics and mechanisms of the reactions of Cl atoms and OH radicals with pentafluorophenol (C₆F₅OH) in 700 Torr total pressure of air or N₂ diluent at 296 ± 2 K. Rate constants k(OH + C₆F₅OH) = (6.88 ± 1.37) × 10^-12 cm³ molecule^-1 s^-1 and k(Cl + C₆F₅OH) = (2.52 ± 0.31) × 10^-11 cm³ s^-1 molecule^-1 in 700 Torr air diluent were determined. In 700 Torr N₂, the rate constant for the reaction of C₆F₅OH with Cl atoms is linearly dependent on the Cl atom concentration. Product studies on this reaction in both 700 Torr air and 700 Torr N₂ diluent show the formation of nonconjugated products. The photolysis constant of C₆F₅OH was determined by 254 nm UV irradiation of a C₆F₅OH and CH₃CHO mixture in 700 Torr air or N₂ at 296 ± 2 K and yielded a photolysis rate constant of J(C₆F₅OH) = (2.83 ± 0.25) × 10^-3 s^-1. Results are discussed with respect to the atmospheric chemistry of other halogenated aromatic species.

Halogen bonding with the halogenabenzene bird structure, halobenzene, and halocyclopentadiene

The ability of the "bird-like" halogenabenzene molecule, referred to as X-bird (XCl to At), to form halogen-bonded complexes with the nucleophiles H₂ O and NH₃ was investigated using double-hybrid density functional theory and the aug-cc-pVTZ/aug-cc-pVTZ-PP basis set. The structures and interaction energies were compared with 5-halocyclopenta-1,3-diene (halocyclopentadiene; an isomer of halogenabenzene) and halobenzene, also complexed with H₂ O and NH₃ . The unusual structure of the X-bird, with the halogen bonded to two carbon atoms, results in two distinct σ-holes, roughly at the extension of the C-X bonds. Based on the behavior of the interaction energy (which increases for heavier halogens) and van der Waals (vdW) ratio (which decreases for heavier halogens), it is concluded that the X-bird forms proper halogen bonds with H₂ O and NH₃ . The interaction energies are larger than those of the halogen-bonded complexes involving halobenzene and halocyclopentadiene, presumably due to the presence of a secondary interaction. © 2019 Wiley Periodicals, Inc.