REACTIONS OF H-, D- AND HD- TRANSFER BETWEEN AN ETHYLENE CATION AND PROPANE CH3CD2CH3 - A STUDY OF KINETICS USING STATE-SELECTED REACTANTS

The dependence on the reactant collisional and internal energy of the total cross sections of hydride-ion (H- or D-) and HD- transfer reacti ons in the system C2D4+ + CH3CD2CH3 was investigated using vibrational ly state-selected reactant ions and guided-beam techniques. The cross sections of formation of C3D6H+ (D- abstraction from position 2 of the target molecule) and C3H5D+ (HD- abstraction from positions 1 and 2) decreased with both collision and reactant ion internal energy as it i s usual for exoergic processes. Formation of C3H5D2+ (H- abstraction f rom position 1) exhibited a much smaller cross section raising from a threshold near the energy zero, suggesting a slightly endoergic proces s, in agreement with thermochemical calculations. The internal energy appears to be about 4 x more effective than the translational energy i n overcoming the endoergicity barrier of this process.