Pulse radiolysis and FT-IR smog chamber experiments were used to investigate the atmospheric fate of C 6 H 5 O(•) radicals. Pulse radiolysis experiments gave σ(C 6 H 5 O(•)) 235 nm = (3.82 ± 0.48) × 10 -17 cm 2 molecule -1, k (C 6 H 5 O(•) + NO) = (1.88 ± 0.16) × 10 -12, and k (C 6 H 5 O(•) + NO 2 ) = (2.08 ± 0.15) × 10 -12 cm 3 molecule -1 s -1 at 296 K in 1000 mbar of SF 6 diluent. No discernible reaction of C 6 H 5 O(•) radicals with O 2 was observed in smog chamber experiments, and we derive an upper limit of k (C 6 H 5 O(•) + O 2 ) < 5 × 10 -21 cm 3 molecule -1 s -1 at 296 K. These results imply that the atmospheric fate of phenoxy radicals in urban air masses is reaction with NO x . Density functional calculations and gas chromatography−mass spectrometry are used to identify 4-phenoxyphenol as the major product of the self-reaction of C 6 H 5 O(•) radicals. As part of this study, relative rate techniques were used to measure rate constants for reaction of Cl atoms with phenol [ k (Cl + C 6 H 5 OH) = (1.93 ± 0.36) × 10 -10 ], several chlorophenols [ k (Cl + 2-chlorophenol) = (7.32 ± 1.30) × 10 -12, k (Cl + 3-chlorophenol) = (1.56 ± 0.21) × 10 -10, and k (Cl + 4-chlorophenol) = (2.37 ± 0.30) × 10 -10 ], and benzoquinone [ k (Cl + benzoquinone) = (1.94 ± 0.35) × 10 -10 ], all in units of cm 3 molecule -1 s -1 . A reaction between molecular chlorine and C 6 H 5 OH to produce 2- and 4-chlorophenol in yields of (28 ± 3)% and (75 ± 4)% was observed. This reaction is probably heterogeneous in nature, and an upper limit of k (Cl 2 + C 6 H 5 OH) ≤ 1.9 × 10 -20 cm 3 molecule -1 s -1 was established for the homogeneous component. These results are discussed with respect to the previous literature data and to the atmospheric chemistry of aromatic compounds.
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Platz et al. (1998) studied this question.