Abstract
Abstract Peroxy radicals play an important role as reaction intermediates in the atmospheric oxidation of volatile organic compounds (VOCs). The rate coefficients for the self-reactions vary by up to six orders of magnitude (e.g. 3.0×10 −17 cm 3 molecule −1 s −1 for t -C 4 H 9 O 2 and 1.5×10 −11 cm 3 molecule −1 s −1 for CH 3 C(O)O 2 ) with, up to now, no clear pattern. This work represents the first rationalisation of peroxy radical self-reaction trends in reactivity. A correlation between the logarithm of the rate coefficient of peroxy radical self-reactions with the stabilisation energy, the difference in the enthalpy of formation of peroxy radicals with that of the tetraoxide adduct {Δ H f (RO 4 R)−2Δ H f (RO 2 )}, is presented. The equation, log 10 k =−{Δ H f (RO 4 R)−2Δ H f (RO 2 )+235.95}/13.32 (where energy is in kJ mol −1 ) is given to predict the room temperature rate coefficients of peroxy radical self-reactions. The correlation was extended to predict rate coefficients for the cross-reactions of peroxy radicals with CH 3 O 2 . Furthermore, favourable comparisons are made between the predicted rate coefficients and very recent studies of complex peroxy radical systems.
Published Version
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