Establish whether the sulfur–oxygen reactivity contrast extends to other aldehyde–thione pairs

Establish whether the distinct hydrogenation behavior identified for thioacetaldehyde (CH3CHS) and acetaldehyde (CH3CHO) also applies to other aldehyde–thione pairs, specifically acrolein (CH2CHCHO) and propenethial (CH2CHCHS).

Background

The study finds that thioacetaldehyde is efficiently transformed through hydrogenation on icy grains, whereas acetaldehyde is comparatively protected from permanent conversion by an abstraction–regeneration cycle. This difference is proposed as a possible explanation for the contrasting abundances of sulfur- and oxygen-bearing molecules in interstellar clouds.

Both acrolein and its sulfur analogue propenethial have been detected in TMC-1, but the paper does not determine whether they exhibit the same contrasting hydrogenation behavior as the CH3CHS/CH3CHO pair. The authors therefore identify the generality of the proposed sulfur–oxygen chemical differentiation as unresolved.

References

It would remain to explain whether the same behavior is expected for other aldehyde (=O) thione (=S) pairs, like acroleine (\ce{CH2CHCHO}) and its sulfur analogue (propenethial; \ce{CH2CHCHS}), both detected in TMC-1 \citep{agundez_o-bearing_2021, cabezas2025discovery}.

— Thioacetaldehyde (CH3CHS) on interstellar ices: a key molecule to unravel two chemical dichotomies in the ISM  (2609.20506 - Mallo et al., 17 Sep 2026) in Section 4, “Discussion”