Radiolysis of methylcyclohexane. III. Pure vapor phase and effects of additives

Abstract

The radiolysis of methylcyclohexane (MCH) vapor was carried out under a variety of conditions. The G-values of the main products a t 110°, extrapolated t o zero dose, are hydrogen (5.2), methylcyclohexene isomers (2.0), ethylene (1.5), methane (1.3), propylene (0.8), and total dimer (0.3). Other products were also measured.The hydrogen yield was reduced t o G = 3.1 b y each of the additives, NzO, SFB, and CC14, and t o G = 1.6 by C2H4. Both DI and ND3 increased the total hydrogen yield above the value in pure MCH. In pure MCH approximately 50% of the ions (G(tota1 ionization) = 4.4) resulted in hydrogen formation, whereas in the presence of D I or NDB, 75y0 of the ions are hydrogen precursors. Thus three different types of positive ions are distinguished in the system: G(M1+) = 2.1,. G(M2+) = 1.3, and G(NC) = 1.0.The average Ion lifetime with respect t o neutralization was s. The ion DI-was therefore stable with respect t o decomposition t o D + I-for a period greater than s under the conditions of the experiments ( N 380 Torr MCH, 110").The yield of methylcyclohexene isomers increased with increasing temperature and increased upon addition of hTD3 or CZH4 to the radiolysis system. The dimer yield was also enhanced by the addition of ND3. This effect was explained by the occurrence of an ionic secondary reaction that destroys methyl~~clohexene and (or) methylcyclohexyl radicals in pure MCH.Approximately 85Yo of the methane is produced by methyl radicals abstracting hydrogen atoms from MCH.

γ-Radiolysis of cyclohexane with electron scavengers. VI. N2O and SF6 as electron scavengers in the vapor phase

“…Hydrogen is reduced to 3.0, G units by the smallest amount of SF6 which could be added. This result is similar to that obtained with the SF6-methylcyclohexane system (18). The yields of the other products studied are affected much less by SF,.…”

The γ-Radiolysis of Ethane. III. The Effect of Density on Ion Scavenging Reactions above the Critical Temperature

“…If G(ions scavenged) is taken as 413 G(HD) then G(HD) = 3.4 at 0.0018 g cc-' represents more ions scavenged than the total ion yield. (A similar observation was made for the gaseous system methylcyclohexane/ammonia-d, (32)). Also in the intermediate density region (0.01-0.2 g cc-') the n-butane yields are much higher than expected.…”

“…The exchange reaction (9) has been observed mass spectrometrically (33) and has been suggested to occur in the gas phase radiolysis (32) with an estimated rate constant of -1012 1 mol-' s-' (33). At 0.0018 g cc-' and 5 m o l z ammonia-d, this reaction will be essentially complete before neutralization occurs.…”

Quenching of the Scintillation from a γ-Irradiated Cyclohexane Solution Containing p-Terphenyl by Electron Scavengers, Positive Ion Interceptors and Some Hydrocarbons

“…Therefore, reactions (12) and (13), should they occur, should be taken into account, along with the series of reactions from (1) to (4). In that case, the reaction (14) should probably be included also: (14) The data obtained in the present paper cannot make a possible decisive choice of a reaction scheme, but they do show that ionic processes seem to play an important role in the scintillation from a cyclohexane solution of p-terphenyl.…”