Ion–Molecule Reactions in the Radiolysis of Ethane

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Abstract
The reactions of ions generated in ethane irradiated with gamma rays have been studied by analyzing the neutral products formed in reactions with ethane and with other molecules. In experiments in the presence of added (C2D5)2CDCD3, for example, it is shown that the following reactions take place: C2H5 ++C2H6→(C4H11 +)*→sec‐C4H9 ++H2; sec‐C4H9 ++(C2D5)2CDCD3→n‐C4H9D+C6D13 +. The intermediate (C4H11 +)* ion can be stabilized by collisions and will then undergo an undetermined reaction (neutralization or proton transfer) to give n‐C4H10 as a product. The over‐all rate constant for reaction of the ethyl ion with ethane is shown to be ≤ 10−10 cm3/molecule·sec. Similarly, it is demonstrated that the reaction C2H3 ++C2H6→C4H9 + leads predominantly to the formation of t‐butyl ions under these conditions: C4H9 ++(C2D5)2CDCD3→(CH3)3CD+C6D13 +. Supplementary experiments performed in a photoionization mass spectrometer demonstrate that ethylene ions undergo a “resonance H2 − transfer” reaction with ethane: C2H4 ++C2D6→C2D4 ++C2H4D2, with a rate constant of 1.1 × 10−10 cm3/molecule·sec. Similarly, the ethane parent ion reacts with ethylene: C2H6 ++C2D4→C2H4 ++C2H2D4.

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