Simulation of the initiated addition of hydrocarbon free radicals and hydrogen atoms to oxygen via a nonbranched chain mechanism

A reaction scheme is suggested for the nonbranched-chain free-radical oxidation of hydrocarbons. The scheme includes the formation of a low-reactivity radical R (e.g., o-CH3C6H4CH2O 4 · ) not participating in further chain propagation. This reaction can effectively compete with reactions of chain propagation via the reactive hydrocarbon radical R· and, as the oxygen concentration in the reaction mixture is increased, begins to inhibit the chain process. The kinetic equation derived from the reaction scheme using the quasi-steady-state treatment provide a description for the nonmonotonic (peaking) dependence of the rate of the chain formation of molecular oxidation products on the oxygen concentration. The energetics of key radical-molecular reactions is considered, and the reaction scheme suggested is applied to the nonbranched-chain hydrogen oxidation involving the low-reactivity radical HO 4 ·