HOT ATOM REACTIONS AND RADIATION-INDUCED EFFECTS IN THE REACTIONS OF RECOIL TRITIUM WITH CYCLOPROPANE

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Abstract
Recoil He3 (n, p) tritium atoms have been reacted with cyclopropane in the gas phase under a variety of experimental conditions. The labeled hydrocarbon and molecular hydrogen products have been separated by gas chromatography and assayed by gas proportional counting.The observed products show a strong dependence upon irradiation dose—cyclopropane is very inert toward reactions with hydrogen atoms and organic radicals, and the labeled olefinic products react preferentially, in effect as scavengers, with the reactive species from radiolysis of the parent molecule.Energetic tritium atoms are able to react with cyclopropane to give labeled cyclopropane as a product without causing isomerization or decomposition of the molecule. The relative yields of cyclopropane and propylene are dependent upon the average collisional de-excitation times, indicating that a fraction of the labeled cyclopropane molecules are decomposing in times of approximately 10−9 seconds. Cyclopropane, propylene, ethylene, hydrogen, and small amounts of allene and methylacetylene are observed as "hot" products in the presence of gaseous free radical scavengers. Many additional compounds are found as the result of free radical and/or radiolysis reactions in the absence of scavengers.The "hot" reactions are explained in terms of the single-step interactions of high kinetic energy tritium atoms with the cyclopropane molecules—the energy for endothermic and high activation energy processes is obtained from the recoil energy. The kinetic energy of the recoil atom at reaction is estimated to be of the order of 130 kcal/mole for some of the observed labeled compounds.

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