Theoretical Study on the Reaction Mechanisms of C2H with O2

The complicated microscopic reaction mechanism of the ethynyl radical with molecular oxygen has been investigated by systematically employing density functional theory and ab initio molecule orbital methods. Geometries and harmonic frequencies of reactants, intermediates, transition states, and products have been investigated at the MP2 with 6-31G(d) and 6-311++G(d,p) basis sets and B3LYP/6-311++G(d,p) theoretical levels, respectively. The QCISD(T) method with the 6-311++G(d,p) basis set has been used in the final single-point energy calculation. The present study reveals that, at room temperature, the main reaction pathways of the reaction of C2H radical with molecule oxygen is C2H + O2 → M1→ TS(1−2) → M2 → TS(2−3) → M3 → TS(3−P2) → CH + CO2. At the same time, several other exothermic pathways have also been characterized.