Abstraction of an H atom from the propyl side chain by hydroperoxyl radicals (HO2) constitutes a central reaction in the low-temperature oxidation of n-propylbenzene (nPB). Herein, we calculate reaction rate constants for H abstraction from primary, secondary and benzylic sites in nPB. Rate of abstraction of a benzylic H atom dominates that of a secondary H atom with negligible abstraction of the primary H atom at T≥600K. We present the reaction enthalpies for 1-phenyl-1-propyl (R1), 1-phenyl-2-propyl (R2) and 1-phenyl-3-propyl (R3) radicals, and compare the computed reaction rate constants and bond dissociation enthalpies with analogous scarce literature values. Addition of HO2 radicals to radical sites in R1, R2 and R3 proceeds in a highly exothermic process and results in the formation of HO2-phenylpropyl adducts. Mapped potential energy surfaces illustrate all plausible exit channels of the three HO2-phenylpropyl adducts. Master equation calculations for the three phenylpropyl+HO2 reactions indicate that direct O-OH bond fission and water elimination control the fate of the adducts leading to the formation of ketonic-type structures. Results from this study should be useful to update kinetic models for the low-temperature oxidation of alkylbenzenes in general.
|Number of pages||11|
|Journal||Combustion and Flame|
|Early online date||3 Dec 2014|
|Publication status||Published - Apr 2015|