Reaction of Acetaldehyde and Acetyl Radical with Atomic and Molecular Oxygen

Article abstract of DOI:10.1021/j100352a032

The reaction of acetaldehyde with atomic oxygen, O(³P), was studied by the discharge-flow-photoinization mass spectrometry method at room temperature (295 +/- 4 K) for the conditions of excess atomic oxygen.The rate constant for reaction 1, CH3CHO + O -> CH3CO + OH, was (3.9 +/- 0.3) x 10^-13 cm³ molecule^-1 s^-1.Branching fractions for the subsequent reactions 2a, CH3CO + O -> CH2CO + OH, and 2b, CH3CO + O -> CH3CO + O -> CH3 + CO2, were determined to be 22 +/- 5 percent and 76 +/- 24 percent, respectively.The experiments in the presence of molecular oxygen show that the ratio of rate constants for reaction 3, CH3CO + O2 + M -> CH3CO3 + M, to reaction 2 is (6.3 +/- 0.5) x 10^-3 .From the rate constant for reaction 3 obtained by McDade et al., the rate constant for reaction 2 was calculated: k₂ = (3.2 +/- 0.7) x 10^-10 cm³ molecule^-1 s^-1.When the concentration of molecular oxygen increased, the yields of both CH3 and CH2CO decreased.From this decrease, the branching fractions for reactions 4a, CH3CO3 + O -> CH2CO + OH + 02, and 4b, CH3CO3 + O -> CH3 + CO2 + O2, were determined: < 10 percent and 27 +/- 25 percent, respectively.A discussion of the other products from CH3CO3 + O is presented.