Kinetics of Cations with C₂ Hydrofluorocarbon Radicals

Abstract

Reactions of the cations Ar, O, CO, and CF with the C radicals CH, HCF, CF, and CF were investigated using the variable electron and neutral density attachment mass spectrometry technique in a flowing afterglow-Langmuir probe apparatus at room temperature. Rate coefficients for observed product channels for these 16 reactions are reported as well as rate coefficients and product branching fractions for the 16 reactions of the same cations with each of the stable neutrals used as radical precursors (the species RI, where R is the radical studied). Reactions with the stable neutrals proceed by charge transfer at or near the collisional rate coefficient where energetically allowed; where charge transfer is endothermic, bond-breaking/bond-making chemistry occurs. While also efficient, reactions with the radicals are more likely to occur at a smaller fraction of the collisional rate coefficient, and bond-breaking/bond-making chemistry occurs even in some cases where charge transfer is exothermic. It is noted that unlike radical reactions with neutral species, which occur with rate coefficients that are generally elevated compared to those of stable species, ion-radical reactivity is generally decreased relative to that of reactions with stable species. In particular, long-range charge transfer appears more likely to be frustrated in the ion-radical systems.

Low-temperature reaction dynamics of paramagnetic species in the gas phase

“…A number of studies involving the reactions of small cations with radicals including N, O, C 2 H 5 , H 2 C 2 F 3 , C 2 F 3 , and C 2 F 5 have been undertaken using flow-based methods. 129,130 While these studies again primarily focused on establishing rate coefficients, some interesting trends in reactivity were identified. For example, the probability of long-range charge transfer was found to be lower in several ion-radical reaction systems than in the corresponding reactions of ions with closed-shell counterparts.…”

Quantum-state-controlled reactions between molecular radicals and ions

“…Even with the considerable potential for increasing our understanding of gas-phase chemical reactions, experimental studies of ion-radical reactions are extremely rare [14][15][16]. This is because laboratory measurements of ion-radical reactions have been notoriously challenging to make, due to the difficulty of creating dense, pure samples of these reactants.…”