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

TL;DR

This study investigates the reaction between CCl+ ions and acetonitrile in a controlled environment, revealing reaction pathways, product branching ratios, and theoretical insights relevant to interstellar and prebiotic chemistry.

Contribution

It is the first to explore CCl+ reactions with nitriles, providing experimental data and quantum chemical analysis of reaction mechanisms and product distributions.

Findings

Primary products are HNCCl+ and C2H3+ with equal probability.

Reaction thermodynamics and potential energy surface are characterized.

Quantum calculations support experimental observations.

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 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 (ISM). Nitriles, in particular, are noted for their relevance in prebiotic chemistry, such as is 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, 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.