Radiolytic processes in mixtures of cyclobutane and perfluorocyclobutane in the gas phase

Abstract

The gas phase radiolysis of mixtures of cyclobutane and perfluorocyclobutane has been studied for systems containing 0–100 per cent of the fluorocarbon. The decomposition of cyclobutane to hydrocarbon products is sensitized by the presence of the fluorocarbon, but the hydrogen yield is directly proportional to the fraction of the energy deposited in the cyclobutane. It is suggested that energy is transferred from excited perfluorocyclobutane to cyclobutane molecules, which subsequently decompose, ultimately forming hydrocarbon products including ethane, ethylene, propane, butenes and others. It appears that unsaturates formed in the radiolysis scavenge free H · atoms, leaving only the unscavengable H 2 yield for detection. It is suggested that electron capture by perfluorocyclobutane, followed by a neutralization reaction with the parent positive ion, leads to efficient rupture of the CF bond and production of HF, as in other fluorocarbon-hydrocarbon mixtures. However, the concomitant interference with the production of H · atoms, seen in other systems, does not lead to a significant lowering of the H 2 yield, which arises largely from other sources in cyclobutane radiolysis. Twenty-eight products have been identified in all, and yields over the entire mixture range have been recorded for twenty-four of them. The majority of the products contain only carbon and hydrogen. Four perfluorocarbon compounds were found, as well as three mixed species containing both fluorocarbon and hydrocarbon moieties. Such products are probably formed by combination of radicals from both parent compounds.