Methanediol CH₂(OH)₂ and hydroxymethyl CH₂OH⁺: key organic intermediates on the path to complex organic molecules

¹ Universidad Autónoma de Chile, Facultad de Ingeniería, Instituto de Ciencias Químicas Aplicadas, Núcleo de Astroquímica & Astrofísica, Av. Alemania 01090, Temuco, Chile
² Universidad Autónoma de Chile, Facultad de Ingeniería, Instituto de Ciencias Químicas Aplicadas, Núcleo de Astroquímica & Astrofísica, Av. Pedro de Valdivia 425, Providencia, Santiago, Chile
e-mail: natalia.inostroza@uautonoma.cl

Received: 10 March 2022
Accepted: 24 May 2022

Abstract

Context. Ab initio molecular dynamics simulations were carried out to study the formation pathways to complex organic molecules when a OH⁺ projectile hit an interstellar dust grain covered only by methanol molecules. The selected target material is a methanol cluster formed by ten units (CH₃OH)₁₀.

Aims. The focus of this paper is the process where methanediol CH₂(OH)₂ and hydroxymethyl CH₂OH⁺, both key organic intermediate molecules, were involved in the formation mechanisms of stable complex organic molecules (COMs).

Methods. We performed Born-Oppenheimer (ab initio) molecular dynamics (BOMD) simulations under the hybrid functional of Head-Gordon ωB97X-D. We used the initial kinetic impact energy of 10, 12, 15, 18, 20, and 22 eV.

Results. We corroborate that CH₂(OH)₂ and CH₂OH⁺ are the main precursors to form molecules such as methoxymethanol CH₃OCH₂OH, the formyl radical HCO, the Criegee biradical CH₂OO, and formaldehyde H₂Co and its elusive HCOH isomer. We discuss the mechanism formation of these complex organic molecules. We compare the formation pathways with previous theoretical results where both key intermediates are present. The pathways in some cases go through CH₂(OH)₂ or undergo by CH₂OH⁺.

Conclusions. We confirm that CH₂(OH)₂ and CH₂OH⁺ play a key role on the path to the formation of abundant H₂CO. These mechanisms can give insight into alternative pathways relevant to understanding experimental processes with key steps within those precursors.