Reactions of methylene in the oxidation process of acetylene with oxygen atoms at 295 K

Reactions of the methylene radical, formed in the oxidation process of acetylene with oxygen atoms at 295 K were studied in a fast flow reactor. Molecular beam sampling and mass spectrometric analysis allowed the monitoring of [CH 2 ] as a function of reaction time. Applying the approach to steady-state analysis on the CH 2 profile, the rate constant k 2 for Reaction [2]: CH 2 +O→CO+2H was found to be (1.3±0.3)×10 −10 molec −1 cm 3 sec −1 . In the presence of an excess amount of acetylene and molecular oxygen, the rate constants k 3 =(1.3±0.3)×10 −12 molec −1 cm 3 sec −1 of Reaction [3]: CH 2 +C 2 H 2 →products and k 4 =(1.7±0.4)×10 −12 molec −1 cm 3 sec −1 of Reaction [4]: CH 2 +O 2 →products were derived. Reaction [3] does not produce C 3 H 4 in a direct step, but yields the radical C 3 H 3 which then forms C 3 H 4 in a further recombination reaction with hydrogen atoms. The rate constant of the reaction of C 3 H 3 with oxygen atoms was found to be 4.7 times larger than that for hydrogen atoms. One of the products of Reaction [4] is the CHO radical and according to a proposed mechanism, the rate constant for its destruction by oxygen atoms is about 33 times larger than that for molecular oxygen.