KINETIC AND MECHANISTIC STUDIES OF THE REACTIONS OF CYCLOPENTYLPEROXY AND CYCLOHEXYLPEROXY RADICALS WITH HO2

The kinetics and mechanism of the reactions c-C5H9O2 + HO2 --> c-C5H9OOH + O2 (1) and c-C6H11O2 + HO2 --> c-C6H11OOH + O2 (2) have been studied using both the flash photolysis/UV absorption and continuous photolysis/FTIR product analysis techniques. End product analysis experiments at 295 +/- 2 K demonstrated that the yield of hydroperoxide was (96 +/- 3) % and (99 +/- 3)% for reactions 1 and 2, respectively, although systematic errors could add an additional 15% uncertainty. Experiments between 248 and 364 K showed that k1 and k2 demonstrated virtually indistinguishable kinetic behavior at all temperatures, with k1/cm3 molecule-1 s-1 = (2.1 +/- 1.3) x 10(-13) exp((1323 +/- 185) K/T) and k2/cm3 molecule-1 s-1 = (2.6 +/- 1.2) x 10(-13) exp((1245 +/- 124) K/T). Absolute uncertainties on kl and k2, including experimental scatter and uncertainties in the analysis parameters, are estimated to be 18%. No dependence of k1 or k2 on pressure between 200 and 760 Torr was found. The room temperature rate constants for reactions 1 and 2 are significantly greater than those measured for other alkylperoxy radicals to date. The reactions of Cl atoms with cyclopentane, Cl + c-C5H 10 --> HCl + c-C5H9 (6) and cyclohexane, Cl + c-C6H12 --> HCl + c-C6H11 (8) were measured relative to that with methanol, Cl + CH3OH --> HCl + CH2OH (4). Neither k6 nor k8 varied significantly with temperature over the range 248-364 K, with k6/cm3 molecule-1 s-1 = (2.3 +/- 0.2) x 10(-10) and k8/cm3 molecule-1 s-1 = (2.4 +/- 0.3) x 10(-10), using k4/cm3 molecules-1 s-1 = 5.7 x 10(-11). Errors are 1-sigma and represent experimental scatter only, unless stated otherwise.