Diastereoselective Formation of Trans-HC(O)SH through Hydrogenation of OCS on Interstellar Dust Grains

Germán Molpeceres,Juan García De La Concepción,Izaskun Jiménez-Serra

doi:10.3847/1538-4357/ac2ebc

Germán Molpeceres, Juan García De La Concepción + Show 1 more

Open Access

https://doi.org/10.3847/1538-4357/ac2ebc

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Abstract

Abstract With the presence of evermore complex S-bearing molecules being detected lately, studies of their chemical formation routes need to keep up the pace to rationalize observations, suggest new candidates for detection, and provide input for chemical evolution models. In this paper, we theoretically characterize the hydrogenation channels of OCS on top of amorphous solid water (ASW) as an interstellar dust grain analog in molecular clouds. Our results show that the significant reaction outcome is trans-HC(O)SH, a recently detected prebiotic molecule toward G+0.693. The reaction is diastereoselective, explaining the apparent absence of the cis isomer in astronomical observations. We found that the reaction proceeds through a highly localized radical intermediate (cis-OCSH), which could be essential in the formation of other sulfur-bearing complex organic molecules due to its slow isomerization dynamics on top of ASW.

Highlights

Sulfur-bearing molecules constitute a fundamental branch of prebiotic chemistry due to the recently gained importance of cysteine C3H7NO2S as a catalyst in the assembly of complex peptides (Foden et al 2020)
Our results show that the significant reaction outcome is trans−HC(O)SH, a recently detected prebiotic molecule toward G+0.693
We found that the reaction proceeds through a highly localized radical intermediate, which could be essential in the formation of other sulfur-bearing complex organic molecules due to its slow isomerization dynamics on top of amorphous solid water

Summary

Introduction

Sulfur-bearing molecules constitute a fundamental branch of prebiotic chemistry due to the recently gained importance of cysteine C3H7NO2S as a catalyst in the assembly of complex peptides (Foden et al 2020). Interstellar environments, cysteine is far from being detected, but other complex organic molecules (COM) of prebiotic importance bearing S have recently been detected, highlighting ethyl mer-. Recently identified in the interstellar medium (i.e, the giant molecular cloud G+0.693, see Rodrıguez-Almeida et al (2021)). OCS is a moderately abundant molecule in the astronomical source where HC(O)SH was detected (ArmijosAbendano et al 2014; Rodrıguez-Almeida et al 2021), second OCS is the only sulfur bearing species positively detected on interstellar ices (Palumbo et al 1997)

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