Ion—Molecule Reactions of Propane Ions with Benzene, 1,3—Butadiene, Hydrogen Sulfide, and Nitric Oxide

Reactions of the principal primary ions from propane, C3H8+, C3H7+, C3H6+, C3H5+, C3H3+, C2H5+, C2H4+, C2H3+, and CH3+ with benzene, 1,3-butadiene, nitric oxide, and H2S were investigated in a tandem mass spectrometer. Reaction mechanisms are deduced for these systems and it is suggested that a relatively long-lived reaction complex is involved for most of these reactions. For the reaction of propyl ions with benzene an unstable adduct C9H13+ was observed which could be stabilized by collision and a unimolecular rate constant of 107sec−1 for its decomposition was estimated from its pressure dependence. In the H2S+–C3D8 and C3D8+—H2S systems charge exchange and deuteronation of H2S are competitive reactions, both proceeding via a long-lived intermediate C3D8H2S+ in which extensive isotopic exchange occurs. The results of this study are correlated with recent radiolysis experiments and it is concluded that these two methods for studing gas-phase ionic reactions are complementary.