Theoretical investigation on the mechanism and kinetics of OH radical with m-xylene

The OH hydrogen abstraction and addition with m-xylene have been studied in the range of 298-1000 K using quantum chemistry methods. The geometries and frequencies of the reactants, transition states and products have been performed at BHandHLYP/6-311++G(d,p) level, and single-point calculation for all the stationary points were carried out at CCSD(T) calculations of the optimized structures with the same basis set. Eight different reaction paths are considered, corresponding to side chain, three possible ring hydrogen abstraction and four kinds different OH addition. The results of the theoretical study indicate that the reaction proceeds almost exclusively through OH addition at room temperature, and is predicted to occur dominantly at the ortho position, and the calculated overall rate constant is 2.60 × 10−11 cm3 molecule−1 s−1, showing the agreement with available experimental data extremely. Despite unimportance at low temperature, at 1000 K ring hydrogen abstraction accounts for about 70% of the total abstraction reaction, and the whole hydrogen abstraction makes up for 3% of the total reaction. This study may provide useful information on understanding the mechanistic features of OH-initiated oxidation of m-xylene.