Reactions of Fe⁺ and FeO⁺ with C₂H ₂, C₂H₄, and C₂H₆: Temperature-dependent kinetics

We present the first temperature-dependent rate constants and branching ratios for the reactions of Fe⁺ and FeO⁺ with C ₂H₂, C₂H₄, and C₂H ₆ from 170 to 700 K. Fe⁺ is observed to react only by association with the three hydrocarbons, with temperature dependencies of T ^-2 to T^-3. FeO⁺ reacts with C₂H ₂ and C₂H₄ at the collision rate over the temperature range, and their respective product branchings show similar temperature dependences. In contrast, the reaction with ethane is collisional at 170 K but varies as T^-0.5, while the product branching remains essentially flat with temperature. These variations in reactivity are discussed in terms of the published reactive potential surfaces. The effectiveness of Fe⁺ as an oxygen-transfer catalyst toward the three hydrocarbons is also discussed.