The kinetics and product state distributions from gas-phase reactions of small atomic and molecular cations with C2H4, C2H3F, 1,1-C2H2F2, C2HF3 and C2F4

Abstract

The reactions of twenty one gas-phase cations with C₂H₃F, 1,1-C₂H₂F₂, C₂HF₃ and C₂F₄ have been studied in a selected ion flow tube at 298 K. The cations are both atomic and molecular with recombination energies in the range 6–22 eV, and the kinetics and branching ratios into product ions are revealed for all the reactions. These data, together with that from an earlier study of reactions of C_xF_y⁺ with these four fluorinated ethenes (J. Phys. Chem. A., 2012, 116, 8119), are compared with the reactions of these ions with C₂H₄, where available. Nearly all the reactions have a rate coefficient close to the collisional value calculated by either Langevin or modified average dipole orientation theories. The products of the reactions of N⁺ and N₂⁺ with C₂H₄ are found to be anomalous, compared to their reactions with the four fluorinated ethenes. The branching ratios into product cations are compared with those from a high resolution (ca. 0.002 eV) photoionisation (hν = 10–22 eV) study of C₂H₃F, 1,1-C₂H₂F₂, C₂HF₃ and C₂F₄ (Phys. Chem. Chem. Phys., 2012, 14, 3935) in order to gauge the importance of electron transfer in ion–molecule reactions. The higher the recombination energy of the cation, the better the agreement between the two sets of product branching ratios. Where there is disagreement at lower recombination energies, it appears that there is more fragmentation of the products in the photoionisation experiment compared to the ion–molecule reactions.