Reaction of ketenes with atomic oxygen

Rate constants for the reaction of atomic oxygen with ketene, and methyl, ethyl, and dimethyl ketene were measured over a temperature range of 230–449 K using the pulse radiolysis resonance absorption system. Over the temperature range of the experiments, the rate data could be fitted by Arrhenius expressions: O+CH2CO, (2.92±0.78)×10−12exp[(−1349±154 cal mol−1)/RT]; O+(CH3)CHCO, (4.79±1.31)×10−12exp[(494.9±163.2 cal mol−1)/RT]; O+(C2H5)CHCO, (5.36±0.83)×10−12exp[(444.6±94.0 cal mol−1)/RT]; O+(CH3)2CCO, (5.92±0.94)×10−12exp[(1131±85 cal mol−1)/RT]; in units of cm3 molecule−1 s−1. The rate constants at room temperature were also determined using a discharge-flow system coupled to a photoionization mass spectrometer. Rate constants obtained are 0.043±0.04, 1.16±0.13, 1.36±0.11, and 6.04±0.64×10−11 cm−3 molecule−1 s−1 for CH2CO, (CH3)CHCO, (C2H5)CHCO, and (CH3)2CCO, respectively. Several reaction products were analyzed by the photoionization mass spectrometer.