The quest for a plausible formation route of formyl cyanide in the interstellar medium: a state-of-the-art quantum-chemical and kinetic approach

TL;DR

This study combines quantum-chemical calculations and kinetic modeling to propose a plausible gas-phase formation pathway for formyl cyanide in the interstellar medium, highlighting temperature-dependent mechanisms.

Contribution

It introduces a validated, detailed reaction mechanism for formyl cyanide formation from aldehydes and radicals, emphasizing the role of gas-phase reactions in space.

Findings

Formyl cyanide can form from aldehydes and cyano radicals in the ISM.

The formation mechanism is effective at low temperatures for formaldehyde.

The mechanism involving acetaldehyde becomes dominant above 200 K.

Abstract

Interstellar complex organic molecules (iCOMs) are assumed to be mainly formed on dust-grain surfaces. However, neutral gas-phase reactions in the interstellar medium (ISM) can play an important role. In this paper, by investigating the reaction between aldehydes and the cyano radical, we show that both formaldehyde (CH$_2$O) and acetaldehyde (CH$_3$CHO) can lead to the formation of formyl cyanide (HCOCN). Owing to accurate quantum-chemical computations followed by rate constant evaluations, we have been able to suggest and validate an effective mechanism for the formation of HCOCN, one of the molecules observed in the ISM. Quite interestingly, the mechanism starting from CH$_2$O is very effective at low temperature, while that involving CH$_3$CHO becomes more efficient at temperatures above 200 K.