Unimolecular and bimolecular reactions in the C4H6+⋅ system: Experiment and theory

Abstract

New experimental data on the metastable reactions of C₄H₆^+⋅ are presented. The bimolecular reactions between C₂H₂^+⋅ and C₂H₄ and between C₂H₄^+⋅ and C₂H₂ have been reinvestigated using a tandem ICR. Total rate constants and branching ratios were measured and isotopic scrambling investigated using deuterium labeling. The experimental data reported here and the PIPECO data of Werner and Baer [J. Chem. Phys. 62, 2900 (1975)] are compared with the predictions of the transition state switching model. Good agreement was found between the predictions of the model and the experimental data. The branching ratios were found to be strong functions of both energy and angular momentum. In the bimolecular reaction between C₂H₂⁺ and C₂H₄ charge transfer appears to occur predominently via a loosely bound intermediate which only samples a small volume of the available C₄H^+⋅₆ phase space.