A computational study of the mechanism for the C₆H₅+ CH₂O reaction

The mechanism for the C₆H₅ + CH₂O reaction has been investigated with hybrid density functional quantum-chemical and statistical theory calculations. The results reveal three possible reaction channels: (1) The abstraction reaction producing C₆H₆ + HCO; (2) addition to the C atom yielding C₆H₅CH₂O and (3) addition to the O atom giving C₆H₅OCH₂. The barriers for these 3 reactions, calculated at the B3LYP/aug-cc-pvtz level of theory using the geometry optimized with B3LYP/cc-pvdz are 0.8, 1.4 and 9.1 kcal mol⁻¹, respectively. The C₆H₅CH₂O radical can fragment to form C₆H₅CHO + H with a barrier of 19.4 kcal mol⁻¹. It can also undergo isomerization reactions ia two cyclic epoxy intermediates to give C₆H₅OCH₂ with a maximum barrier of 20.4 kcal mol⁻¹. Transition-state theory calculations using the predicted energy barriers and structures for the rate constants of the abstraction reaction (1) lead to very good agreement with our recently measured values, while the result of RRKM calculations for the isomerization/decomposition of C₆H₅OCH₂ to C₆H₅CHO + H also agrees quantitatively with available experimental data.