Recoil He3 (71, p) tritium atoms have been reacted with cyclopropane in the gas phase under a variety of experimental conditions. The labeled hydrocarbon and molecular hydrogerl products have been separated by gas chromatography and assayed by gas proportional counting.The obser\;ed products show a strong dependence upon irradiation dose-cyclopropane is very inert to\\ra~-cl reactions with hydrogen atoms and organic radicals, and the labeled olefinic products react preferentially, in effect as scavengers, \vith the reactive species from radiolysis of the parent molecule.Energetic tritium atoms are able to react \\.ith cyclopropane to give labeled cyclopropane a s a product without causing isonierization or decomposition of the molecule. The relative yields of cyclopropane and propylene are dcpendent LIPOII the average collisional de-excitation times, indicating that a fraction of the labeled cyclopropane molecules are decomposing in times of approxirnatel), 10-"seconds. Cyclopropane, propylene, ethylene, hydrogen, and srnall 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 atorns with the c).clopropane molecules-the energy for endothermic and high activation energy processes is obtained from the recoil energy. The kinetic energy of the recoil atom a t reaction is estimated to be of the order oc 130 Itcal/mole for some of the observed labeled compo~~nds.

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