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

Abstract

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.

Reactions of Acetonitrile with Trapped, Translationally Cold Acetylene Cations

“…Because of this overlap, it is important to understand how calcium is reacting with CH 3 CN in order to correctly model the formation and depletion of C 3 H 4 + . The reaction of Ca + + CH 3 CN has been previously studied and only produces m / z 66 CaCN + . We verified that there were no interfering mass products with the current reaction by reacting Ca + with CH 3 CN without any acetylene present and concluded no statistically significant differences of the formation of CaCN + from the reaction when acetylene cations are present.…”

“…Kinetic data are measured using a LIT radially coupled to a TOF-MS. The LIT TOF-MS has been described in detail elsewhere, ,,, and only a brief summary of the features pertinent to the current experiment are given here. Acetylene cations are produced using a (1 + 1) resonance-enhanced multiphoton ionization scheme.…”

Interaction of CH3CN and CH3NC with He: Potential Energy Surfaces and Low-Energy Scattering

“…Finally, we note that the reactivity of methyl cyanide with molecular ions at low temperature has been studied experimentally by several groups. − Ideally, this requires molecules that are cooled prior to the reaction. Several approaches to produce cold beams of CH 3 CN have been reported, ,, which allow the production of CH 3 CN in the ground rotational state .…”

Charge Transfer Reactions between Water Isotopologues and Kr+ ions

“…There have been a number of previous studies into ion–molecule reaction systems under comparable experimental conditions. The astrochemically interesting reaction between sympathetically cooled CCl + ions and thermal CH 3 CN neutrals was recently studied within Ca + Coulomb crystals, at an effective reaction temperature of 160 K. The experimental rate coefficient was found to be in agreement with predictions from ADO capture theory . For the reaction of non-polar C 2 H 2 with CCl + ions, the experimental results were successfully described by the Langevin capture model .…”