Isotope-specific reactions of acetonitrile (CH₃CN) with trapped, translationally cold CCl

The gas-phase reaction of CCl⁺ with acetonitrile (CH₃CN) is studied using a linear Paul ion trap coupled to a time-of-flight mass spectrometer. This work builds on a previous study of the reaction of CCl⁺ with acetylene [K. J. Catani et al., J. Chem. Phys. 152, 234310 (2020)] and further explores the reactivity of CCl⁺ with organic neutral molecules. Both of the reactant species are relevant in observations and models of chemistry in the interstellar medium. Nitriles, in particular, are noted for their relevance in prebiotic chemistry and are found in the atmosphere of Titan, one of Saturn's moons. This work represents one of the first studied reactions of a halogenated carbocation with a nitrile and the first exploration of CCl⁺ with a nitrile. Reactant isotopologues are used to unambiguously assign ionic primary products from this reaction: HNCCl⁺ and C₂H₃ ⁺. Branching ratios are measured, and both primary products are determined to be equally probable. Quantum chemical and statistical reaction rate theory calculations illuminate pertinent information for interpreting the reaction data, including reaction thermodynamics and a potential energy surface for the reaction, as well as rate constants and branching ratios for the observed products. In particular, the reaction products and potential energy surface stimulate questions regarding the strength and role of the nitrile functional group, which can be further explored with more reactions of this class.