Unimolecular decomposition of [80Br]bromocyclopropane formed by reaction of recoil bromine atoms with cyclopropane or with bromocyclopropane

Abstract

The reactions of recoil bromine, from the ⁷⁹Br(n,γ)⁸⁰Br reaction, with cyclopropane and with bromocyclopropane have been investigated as a function of total pressure. The primary product, cyclo-C₃H₅⁸⁰Br, of the ⁸⁰Br-for-H reaction in the former and of the ⁸⁰Br-for-Br reaction in the latter, is highly excited and undergoes unimolecular decomposition to CH₂CHCH₂⁸⁰Br. The decomposition product from the former reaction still has enough energy to decompose further to the [⁸⁰Br]bromomethyl radical which is isolated as CH₂⁸⁰BrI in the presence of I₂ scavenger. On the other hand most of the CH₂CHCH₂⁸⁰Br from the ⁸⁰Br-for-Br reaction is stabilized either by collisional de-excitation or release of the ⁸⁰Br atom.

From the potential energy diagrams of these decomposition pathways, the median excitation energies of the primary products are estimated to be greater than 4 eV for the ⁸⁰Br-for-H reaction and 2–4 eV for the ⁸⁰Br-for-Br reaction.