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

Abstract

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.

Theoretical insights into the gaseous and heterogeneous reactions of halogenated phenols with ˙OH radicals: mechanism, kinetics and role of (TiO2)nclusters in degradation processes

“…Similar negative temperature-dependent results from a negative activation energy were observed in the reaction of tris(2-chloroisopropyl) phosphate with ˙OH radical. 55 Table S2 (ESI†) shows that the overall rate constant for the ˙OH + C 6 H 5 OH reaction calculated at the CCSD(T)/aug-cc-pVDZ//M06-2X/6-311G(d,p) level was 6.03 × 10 −12 cm 3 molecule −1 s −1 at 296 K, perfectly matching the (6.88 ± 1.37) × 10 −12 cm 3 molecule −1 s −1 deduced by Hasager et al 44 Our results further confirmed that the adopted level was reliable for computing the title reactions, and the calculated results were credible. Tables S3 and S4 (ESI†) show that the rate constants of ˙OH + C 6 Cl 5 OH and ˙OH + C 6 Br 5 OH were 6.27 × 10 −12 and 6.99 × 10 −12 cm 3 molecule −1 s −1 at 296 K. Thus, the rate constant of the substitution of bromine atoms at room temperature was the largest one among the three species, similar to the results of acyl halides.…”

“…In the photocatalytic degradation of pollutants, OH is the most important reactive species, significantly promoting the photocatalytic oxidation efficiencies of gaseous pollutants. 42,43 In experiments, the initial rate constant at room temperature of the OH-radical induced homogeneous degradation of C 6 X 5 OH (X = F, Cl, Br) has been reported by Hasager et al 44 and Fang et al, 45 which has verified the important role of OH radicals in their environmental removal. Nevertheless, the experimental inference still requires theoretical support because the produced highly active intermediates and transition states have short lifetimes, and they are almost impossible to be represented in an experiment.…”

A new theoretical investigation on ·OH initiated oxidation of acephate in the environment: mechanism, kinetics, and toxicity

“…where [OH] is the $OH concentration, which is 1 Â 10 6 molecule cm −3 in the atmospheric troposphere, 45 and k tot is 7.86 Â 10 −10 cm 3 per molecule per s at 298 K obtained in this work. The lifetime is calculated to be 0.35 h at 298 K, implying that acephate is quickly oxidized by OH radicals in the atmosphere.…”

“…Furthermore, in order to reveal the ·OH initiated degradation of acephate in the atmosphere, the lifetime ( τ ) was calculated to estimate the reaction time in the atmosphere with the following formula:where [OH] is the ·OH concentration, which is 1 × 10 6 molecule cm −3 in the atmospheric troposphere, 45 and k tot is 7.86 × 10 −10 cm 3 per molecule per s at 298 K obtained in this work. The lifetime is calculated to be 0.35 h at 298 K, implying that acephate is quickly oxidized by OH radicals in the atmosphere.…”

On single-electron magnesium bonding formation and the effect of methyl substitution

“…In the present work, we aim to gain a fundamental understanding of the interaction between magnesium salt molecules and free radicals since the latter are known to play a crucial role in chemistry, especially organic chemistry, 39,40 atmospheric chemistry 41,42 and biochemistry. 43,44 By using quantum chemical calculations, the formation of single-electron magnesium bond between MgX 2 (X ¼ F, H) and a series of alkyl radicals (methyl, ethyl, isopropyl, and tertiary butyl) was characterized in detail and compared with other noncovalent interactions.…”