A computational study of the mechanism for the C ₆ H ₅ + CH ₂ O reaction

The mechanism for the C ₆ H ₅ + CH ₂ O 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 C ₆ H ₆ + HCO; (2) addition to the C atom yielding C ₆ H ₅ CH ₂ O and (3) addition to the O atom giving C ₆ H ₅ OCH ₂ . 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 C ₆ H ₅ CH ₂ O radical can fragment to form C ₆ H ₅ CHO + H with a barrier of 19.4 kcal mol ^-1 . It can also undergo isomerization reactions via two cyclic epoxy intermediates to give C ₆ H ₅ OCH ₂ 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 C ₆ H ₅ OCH ₂ to C ₆ H ₅ CHO + H also agrees quantitatively with available experimental data.