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Experimental and theoretical investigation of the reaction of RO 2 radicals with OH radicals: Dependence of the HO 2 yield on the size of the alkyl group
Author(s) -
Assaf Emmanuel,
Schoemaecker Coralie,
Vereecken Luc,
Fittschen Christa
Publication year - 2018
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.21191
Subject(s) - radical , chemistry , yield (engineering) , adduct , alkyl , photochemistry , moiety , photodissociation , medicinal chemistry , computational chemistry , organic chemistry , thermodynamics , physics
Abstract The HO 2 yield in the reaction of peroxy radicals with OH radicals has been determined experimentally at 50 Torr helium by measuring simultaneously OH and HO 2 concentration time profiles, following the photolysis of XeF 2 in the presence of different hydrocarbons and O 2 . The following yields have been obtained: ϕCH 3 O 2 = (0.90 ± 0.1), ϕ C 2 H 5 O 2 = (0.75 ± 0.15), ϕ C 3 H 7 O 2 = (0.41 ± 0.08), and ϕ C 4 H 9 O 2 = (0.15 ± 0.03). The clear decrease in HO 2 yield with increasing size of the alkyl moiety can be explained by an increased stabilization of the trioxide adduct, ROOOH. This has been confirmed by ab initio and Rice–Ramsperger–Kassel–Marcus master equation calculations. Extrapolation of the experimental results to atmospheric conditions shows that the stabilized adduct, ROOOH, is the nearly exclusive product of the reaction between OH radicals and peroxy radicals containing more than three C‐atoms. The fate and possible impact of these species is completely unexplored so far.