Interstellar Enolization-Acetaldehyde (CH₃ CHO) and Vinyl Alcohol (H₂ CCH(OH)) as a Case Study

Area of Science:

• Astrochemistry
• Interstellar Medium Chemistry
• Organic Chemistry

Background:

• Enols, thermodynamically less stable tautomers, typically do not form in cold gas-phase environments.
• Laboratory studies show keto-enol pairs form in interstellar analog ices, but only acetaldehyde-vinyl alcohol has been detected in space.
• Enols' reactivity with electrophiles is key to understanding molecular complexity in the interstellar medium, comets, and meteorites.

Purpose of the Study:

• Investigate the enolization of aldehydes in interstellar ices via interaction with galactic cosmic rays (GCRs).
• Utilize energetic electrons as proxies for secondary electrons generated by GCRs in interstellar ices.

Main Methods:

• Irradiation of acetaldehyde ices with energetic electrons.
• Simulation of secondary electron interactions from GCRs in interstellar ice analogs.

Main Results:

• Galactic cosmic rays (GCRs) can induce the enolization of acetaldehyde in interstellar ices.
• Both intra- and intermolecular processes contribute to enol formation.
• Enols are likely ubiquitous in the interstellar medium.

Conclusions:

• Enols should be widespread in the interstellar medium and detectable by radio telescopes like ALMA.
• Detection of enols will enable their use as tracers for non-equilibrium ice chemistry.
• This can help constrain fundamental reaction mechanisms within interstellar ices.