Reactions of the gaseous carbonium ions from the decay of [1,2-3H2]-cyclopentane

Abstract

The nature and the reactions of the gaseous ions formed from the β decay of a tritium atom in cyclopentane were investigated by a tracer technique. [1,2-³H₂]Cyclopentane was allowed to decay in cyclopentane, at pressures ranging from 10 to 700 Torr, and the radioactive decay products were analysed by radio gas-chromatography. The results suggest that over 90% of the β transitions lead to the formation of C₅H₈T⁺ daughter ions with little or no excitation energy, which retain their cyclic structure unchanged. The small fraction of the ions that receive a significant excitation energy from the nuclear transition undergo isomerization and fragmentation processes, which lead to linear C₁—C₅ tritiated hydrocarbons. The results support the conclusions reached in previous kinetic and mass spectrometric studies on the distribution of the excitation energy within the daughter ions from the decay of simple tritiated molecules. The mechanisms responsible for the formation and the reactions of the gaseous carbonium ions are discussed, and compared with the corresponding processes observed in the solution chemistry of the cyclopentyl cation.