Radiolysis of acetylene-nitrous oxide mixtures and the effect of carbon dioxide

Abstract

Acetylene-nitrous oxide mixtures were irradiated to low dose levels (≈4·1 × 10 19 eV g −1) with 60Co γ-radiation. Nitrogen was formed, increasing with nitrous oxide concentration to a limiting value G(N 2) ∞ = 18·2 ± 1·7 [equivalent to 4·7 × G(electron)], for mixtures containing around 20% N 2O. There was a small yield of carbon monoxide [ G(CO) = 0·32 ± 0·08], and the polyacetylene was oxygenated. Addition of sulphur hexafluoride prevented formation of nitrogen and when carbon dioxide was added to the acetylene-nitrous oxide system, nitrogen yields were reduced, tending to a lower limit around G(electron). The results can be explained on the basis of electron capture by nitrous oxide, followed by a short-chain process initiated by reaction of O − ion with acetylene. Estimated relative rate constants for the proposed mechanism are given. Benzene was also formed, and the initial yield [ G(C 6H 6) = 11·1 ± 1·2] was not affected by electron scavenging, indicating that ion-neutralization reactions are not involved in the cyclization process.