A Kinetic and Mechanistic Study of the Reaction of Neopentylperoxy Radicals with HO2

Article abstract of DOI:10.1021/j100196a037

The kinetics and mechanism of the reaction between neopentylperoxy radicals and hydroperoxy radicals: neo-C5H11O2 + HO2 -> neo-C5H11OOH + O2 (1), have been studied between 248 and 365 K, using the flash photolysis/time-resolved UV absorption and the blacklamp photolysis/FTIR product analysis techniques.The rate constant for reaction 1, k₁, is significantly larger than that for smaller primary alkylperoxy radicals, with k₁/cm³ molecule^-1 s^-1 = (1.43 +/- 0.46) * 10^-13 exp((1380 +/- 100)K/T), giving k₁/cm³ molecule^-1 s^-1 = (1.5 +/- 0.4) * 10^-11 at 298 K.Consideration of possible random and systematic errors results in absolute uncertainties of 25 percent in k₁ over the experimental temperature range.Product analysis studies at 196 +/- 2 K show that the yield of hydroperoxide from reaction 1 is (92 +/- 2) percent; possible systematic errors may add an additional 15 percent uncertainty.It is concluded that the rate constant for the generic reaction RO2 + HO2 used in the modeling of non-methane hydrocarbon atmospheric chemistry should be increased.The rate constant for the reaction of chlorine atoms with neopentane, Cl + neo-C5H12 -> HCl + neo-C5H11 (3), was also measured relative to that for the reaction of chlorine atoms with methanol, Cl + CH3OH -> HCl + CH2OH (5).Within experimental error, k₃ is independent of temperature over the range 248-366 K, with K₃/cm³ molecule^-1 s^-1 = (1.16 +/- 0.05) * 10^-10, using k₅/cm³ molecule^-1 s^-1 = 5.7 * 10^-11.The error in k₃ does not include uncertainties in k₅.Errors are 1?.