The Dissociation of Cyclopropane under Electron Impact

Abstract

The electron‐impact‐induced dissociations of cyclopropane are determined from the appearance of potentials of the several ions formed. In general, the dissociations involve a considerable amount of atomic rearrangement, and the evidence points to the opening of the carbon ring in the formation of the C₃ ions. The energy required to convert cyclopropane to ethylene and methylene is found to 77 kcal/mole, from which it is estimated that the C–C bond dissociation energy in cyclopropane is at least 50 kcal/mole. The unexpectedly good agreement of the values of the heat of formation of an ion formed by electron impact from several different sources is noted, and a question is raised as to the role of activation energies in the electron‐impact dissociations of polyatomic molecules.