To form or not to form a reaction complex: exploring ion–molecule reactions between C3H4 isomers and Xe+ and O2+

Abstract

Ion–molecule reactions are an essential contributor to the chemistry of a diverse range of environments. While a great deal of work has been done to understand the fundamental mechanisms driving these reactions, there is still much more to discover. Here, we expand upon prior studies on ion–molecule reactions involving two isomers of C₃H₄, allene (H₂C₃H₂) and propyne (H₃C₃H). Specifically, we probe the previously observed isomeric dependent reactivity of these molecules by reacting them with two ions with nearly identical ionization potentials, Xe⁺ and O₂⁺. Our goal is to determine if the isomer-dependent reaction mechanisms previously observed are universal for C₃H₄ or if they depend on the ion character as well. Through the combination of experimental measurements and theoretical calculations, we found that both isomeric structure and identity of the ion contribute to the propensity of a reaction complex forming or for only long-range charge transfer to occur.