Electron spin resonance study of the reaction between oxygen atoms and acetylene

Abstract

The reaction between O atoms and acetylene at room temperature has been studied by following the variation of the O atom, H atom, and OH radical concentrations with time using gas-phase e.s.r. The results conform with the basic mechanism: O + C₂H₂→ CH₂+ CO (1) O + CH₂→ CO + 2H (2) CH₂+ C₂H₂→ C₃H₄(3) H + C₂H₂→ C₂H₂+½H₂. (4) The [O] profiles agree with the results of previous investigations but the [H] profiles indicate that the estimates of the overall stoichiometry are too high. The present data give values for k₁ of 1.1 ± 0.1 × 10⁸ l mol^–1 s^–1 and for k₂/k₃ of 2.6 ± 0.3.

OH radicals appear to be produced by the reaction O + CH₂→ CH + OH (2a) where k_2a/k₂= 0.06 ± 0.02, and to decay by the reaction OH + C₂H₂→ H₂O + C₂H (5) where a value for k₅ may be estimated.