Cw laser absorption study of the reactions of phenyl radicals with NO, NO2, O2 and selected organics between 298-404 K

Article abstract of DOI:10.1002/bbpc.19890931205

The applied aspect concerning the reactivity of phenyl relates to its suggested participation in the formation mechanisms of polycyclic aromatic hydrocarbons (PAHs) and of soot. In the present paper we report the first application of a direct detection method of phenyl in the gas phase. It will be shown that by using the 488 nm laser line absorption in the $UNK²A₁ - $UNK²B₁ transition phenyl can be detected with sufficient sensitivity to enable kinetic investigations of its reactions. To our knowledge this has not been achieved before. Rate constant for the reactions of phenyl (C₆H₅) radicals with NO, NO₂, O₂, C₂H₄, 2-butene, benzene, toluene and CCl₄ have been determined using a combined laser photolysis laser absorption technique. Phenyl radicals were generated by 248 nm excimer laser photolysis of C₆H₅X, where X = Cl, Br and NO. Their temporal behaviour was monitored using cw-laser line absorption in the $UNK²A₁ - $UNK²B₁ transition at 488 nm. The magnitude of the rate coefficients k₁ and k₂ and their negative temperature dependence suggest that the reactions between phenyl and NO/NO₂ occur as radical recombination and/or (in the case of NO₂) as O-atom metathesis reaction. The apparent low reactivity of phenyl with O₂ is likely to be caused by insufficient thermal stability of the phenylperoxi radical.