DFT study on the abstraction and addition of Cl atom with toluene

Density functional theory and conventional transition state theory (TST) are employed to investigate the reaction of Cl with toluene. Eight different reaction paths are considered, corresponding to side chain, three possible ring hydrogen abstraction and four kinds of different Cl addition. The calculated results indicate that the reaction proceeds almost exclusively through hydrogen abstraction at room temperature, and is predicted to occur dominantly at the side chain position, and the calculated overall rate constant at the CCSD(T)/6-311++G(d,p)//BHandHLYP/6-311++G(d,p) is 6.49 × 10−11 cm3 molecule−1 s−1, showing a reasonably good agreement with the available experimental results. Although negligible at low temperature, at 1000 K ring hydrogen abstraction accounts for about 20% of the total abstraction reaction, and the total hydrogen abstraction makes up for about 98% of the total reaction above 800 K, indicating that hydrogen abstraction is the dominant channel for the Cl-toluene reaction at high temperatures, which is different from the OH-toluene reaction. This study may provide useful information on understanding the mechanistic features of Cl-initiated oxidation of toluene.