An Ion Cyclotron Resonance Study of the Structure of C₃H₆+ and the Mechanism of its Reaction with Ammonia

The reactions of ammonia and ammonia- and the C₃H₆ radical cation, produced in the ionization of cyclopropane and in the unimolecular fragmentation of tetrahydrofuran, and the C₃H₄D₂ radical cation from tetrahydrofuran-2, 2, 5, 5-rf₄ were investigated in detail. The C₃H₆ ⁺ ion reacts with ND3, and the elements of C₂H₅ are lost as C₂H₄D indicating no scrambling of hydrogen among the carbon and nitrogen atoms of the collision complex. Furthermore, the label distributions in the product ions produced by C3H₄D₂ ⁺ and NH₃ or ND₃ demonstrate that the structure of C₃H₄D²⁺ is one in which the three carbon atoms have become equivalent. The results also show that there is essentially no randomization of hydrogen atoms in the primary C₃H₄D²⁺ or in the intermediate complex formed in the reaction with ammonia.