A semi-empirical correlation for the rate coefficients for cross- and self-reactions of peroxy radicals in the gas-phase

• Published in: Atmospheric environment (1994) 2005-02, Vol.39 (4), p.763-771
• Main Authors: Shallcross, Dudley E., Teresa Raventos-Duran, M., Bardwell, Max W., Bacak, Asan, Solman, Zachary, Percival, Carl J.
• Format: Article
• Language: English
• Subjects: Applied sciences; Atmospheric pollution; Correlations; Cross-reaction; Exact sciences and technology; Kinetics; Peroxy radicals; Pollutants physicochemistry study: properties, effects, reactions, transport and distribution; Pollution; Self-reaction
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/j.atmosenv.2004.09.072

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 4H 9O 2 and 1.5×10 −11 cm 3 molecule −1 s −1 for CH 3C(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 4R)−2Δ H f(RO 2)}, is presented. The equation, log 10 k=−{Δ H f(RO 4R)−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 3O 2. Furthermore, favourable comparisons are made between the predicted rate coefficients and very recent studies of complex peroxy radical systems.