Methylacetylene (CH3CCH) and propene (C3H6) formation in cold dense clouds: a case of dust grain chemistry

TL;DR

This paper reviews the formation mechanisms of methylacetylene and propene in cold dense clouds, emphasizing the role of dust grain surface chemistry over gas-phase reactions.

Contribution

It introduces a surface hydrogenation pathway on dust grains as the primary formation process for these hydrocarbons in interstellar environments.

Findings

Gas-phase reactions cannot account for methylacetylene and propene abundance.

Surface hydrogenation of C3 on dust grains explains their formation.

Highlights the importance of dust grain chemistry in astrochemical models.

Abstract

We present an extensive review of gas phase reactions producing methylacetylene and propene showing that these relatively abundant unsaturated hydrocarbons cannot be synthesized through gas-phase reactions. We explain the formation of propene and methylacetylene through surface hydrogenation of C3 depleted onto interstellar ices, C3 being a very abundant species in the gas phase.