Recoil tritium reactions with spiropentane: primary hot interactions and secondary unimolecular decomposition

Abstract

In recoil tritium reactions with spiropentane, the primary products, including those form abstraction, substitution and ring-opening processes, were all measured. Spiropentane-t molecules, excited by T-for-H substitution, underwent unimolecular processes by two different routes: one is the direct decomposition process and the other is the consecutive isomerization-decomposition process. In the former case the excited spiropentane-t molecules decomposed directly to C₂H₃T and C₃H₃T, while in the latter case the excited molecules isomerized to excited methylenecyclobutane-t molecules which then decomposed to give the same end products. The unimolecular nature of the reaction was verified by pressure studies from 79 to 4462 torr. The C₂H₃T/C₃H₃T ratios from these samples with the total pressure lower than 300 torr were all approximately equal to 1.0. This leads to the conclusion that nonrandomized decomposition is only a minor or negligible process in the employed pressure range. However, as the total pressure of the system became higher than 300 torr, this ratio began to deviate from unity. The ratio became lower than unity as the total pressure was increased. At the highest total pressure (4462 torr) this ratio is 0.76±0.02 compared to that of 0.90±0.02 at 1610 torr. The presence of this deviation confirmed that a small but finite fraction of the energy nonrandomized decomposition was actually present in the system which became more obvious at high pressures.