Thermochemical and kinetic studies of H-abstraction reaction of benzofurans and benzodioxins by H-atoms

• H-abstraction reactions by H-atoms from selected OPAHs. • PES explored with DFT methods. • Energetics calculated at the UCCSD(T)-F12/CBS approach. • Determination of the kinetic parameters over the temperature range of 500–2000 K. • Effect of the nature of H-abstracted atom on rate constants in flame conditions. The thermo-kinetic data of the H-abstraction of benzofurans (benzofuran and dibenzofuran) and benzodioxins (1,4-benzodioxin and dibenzo-p-dioxin) have been obtained by the CCSD(T)-F12/CBS//CAM-B3LYP/6–311++G(d,p) method. Based on the Bonding Dissociation Energies (BDE) we have observed a stabilization effect exerted by the O-atom on the H-atoms located in β-position of it, thereby increasing their BDEs. In line with these BDEs, we have classified the H-atoms into four groups: group 1 , H-atoms in the benzene ring unaffected by the stabilization effect of the oxygen atom; group 2 , H-atoms in the benzene ring under the influence of the stabilization effect of the oxygen atom; group 3 , H-atoms positioned in the dioxin ring and group 4 , H-atoms located in the furan ring. We have calculated and evaluated the kinetic constants for the H-abstraction reactions for each of these H-atoms thereby deducing the average values for each type of the H-abstracted.