THE PRESSURE-DEPENDENCE OF THE NO2 PRODUCT YIELD IN THE REACTION OF NO3 RADICALS WITH SELECTED ALKENES

An explanation is given For the difference in pressure dependences of the NO2 product yield in the reactions NO3 + alkene and NO3 + 1,3-alkadiene including styrene. A simple model is used to describe the decomposition over stabilization ratio for the chemically activated intermediate nitrooxy-alkyl radical. It is shown that the resonance stabilization of this radical in the case of conjugated olefins is sufficiently high to account for the difference observed. The model is applied to experimental data from the reactions of NO3 with trans-2-butene, 2,3-dimethyl-2-butene, 2-methyl-1,3-butadiene, 2,3-dimethyl- 1,3-butadiene, and styrene. Kinetic parameters for the decomposition reaction of the intermediate radicals into NO2 and epoxide are estimated and consequences for their reactions under tropospheric conditions are discussed.