Effect of Additives on the Ionic Reaction Mechanism in the Radiolysis of Methane

This work describes the reactions of the ions C2H5+ and CH5+ with C3D8, C4D10, C5D12, as well as the reactions of C2D5+ and CD5+ with C3H8. It is shown that ethyl ions undergo a hydride transfer reaction with all higher hydrocarbons even though they are present at a concentration of only 0.01%. The scavengers NO and O2 react with ethyl ions effectively, provided the relative concentration of the higher hydrocarbons is less than that of the free radical scavengers. A proton-transfer reaction between CH5+ and higher hydrocarbons followed by a rapid decomposition of the protonated hydrocarbon into a carbonium ion and a neutral alkane molecule is shown to occur. From the data it can be deduced that at a methane pressure of 48 cm G(C2H5+) =0.9±0.2 and G(CH5+) =1.9±0.2. It is concluded that in earlier published studies of the radiolysis of methane, the C2H5+ and CH5+ ions reacted with the accumulated products or with the added free radical scavengers, thus excluding the neutralization of these two species.