Formation of CH3CHO in the combination of CH3 with CHO

Abstract

By reacting atomic hydrogen with mixtures of CH₃Br and CO to generate CH₃ and CHO radicals simultaneously, the formation of CH₃CHO by combination of CH₃ with CHO has been observed. For experiments at 473 K, it is shown that the rate coefficient for this reaction is twice the product of the square roots of those for mutual termination of CH₃ and CHO, to within the error limits. With this approximation, a model reaction scheme has been developed to analyse the effects of varying the pressures of CH₃Br and CO; thereby the yields of CH₃CHO produced by the combination of CHO with CH₃ have been derived in the temperature range 373–473 K, with a total pressure of 600 Torr.

The yield appears to decrease slightly with increasing temperature, falling from ca. 0.55 at 373 K to ca. 0.42 at 473 K. The competing reaction generates CH₄ plus CO, and it is argued that the two reactions proceed through different transition states.

By computer simulation, it is shown that deviations from the model at the lower temperatures are due to participation of CH₃CO.