Methylperoxy radicals, atmospheric reaction

Table 6-12. Comparison of Atmospheric Reaction Rates for Methylperoxy Radicals ...

K yields a value five times larger than that previously assumed for atmospheric modelling calculations. Further quantitative studies of reactions of atmospheric importance include measurements of the temperature dependences of process (24) and of the recombination rate of methylperoxy radicals with N02, and... 

At night the thermal decomposition of PAN in an atmosphere with a relatively high mixing ratio of NO (e.g.,10 ppb) can initiate reaction 5.96 that converts NO to NO2 and produces a methylperoxy radical, which itself may convert another NO to NO2 and produce a molecule of formaldehyde, reaction 5.45. This sequence could lead to a reservoir of photo-chemically active species when the Sun rises. 

The methylperoxy radical (and probably other peroxy radicals) reacts very rapidly with NO (4.41) relative to hydrogen abstraction (4.40), so only in very clean environments will the latter reaction occur to a significant extent (McFarland et al., 1979 Hanst and Gay, 1983). In polluted atmospheres, nitrogen oxides interfere with several other of the above reactions, leading to the formation of nitrate and peroxy-nitrate esters (see Section 4.A.4). 

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