# Isomer-Specific Branching Ratios in the Formation of Cyanopropene (C3H5CN) through the C3H6 + CN Reaction under Interstellar Conditions

## TL;DR

This study explains how different cyanopropene isomers form in space through reactions involving propene and the cyano radical.

## Contribution

The paper provides isomer-specific branching ratios for cyanopropene formation under interstellar conditions using high-accuracy computational methods.

## Key findings

- All observed cyanopropene isomers can form via the C3H6 + CN reaction.
- Vinyl cyanide is the dominant product compared to cyanopropene isomers.
- Predicted branching ratios align with observations, suggesting gas-phase chemistry as the main formation pathway.

## Abstract

We investigated the
reaction of propene (C3H6) with the cyano radical
(CN) in light of the recent
detection of
five cyanopropene isomers in TMC-1. To provide reliable branching
ratios, we characterized the stationary points on the potential energy
surface using the high-accuracy jun-ChS-F12 method. The resulting
energetics were then employed to derive temperature-dependent rate
constants. Our calculations show that the formation of all observed
cyano derivatives is feasible through this reaction, although it is
secondary compared to the dominant formation channel of vinyl cyanide
(C2H3CN). The predicted branching ratios are
in good agreement with the observations, with the discrepancies prompting
further investigation on the destruction mechanisms of the different
isomers. Overall, this work supports a scenario in which these cyano
derivatives in TMC-1 arise primarily from pure gas-phase chemistry.