Interstellar hide and go seek: C₃H₄O. There and back (again).

Area of Science:

• Astrochemistry
• Theoretical Chemistry
• Spectroscopy

Background:

• The C3H4O molecular species presents an astrochemical puzzle, with over 60 possible isomers, yet only acrolein identified in the interstellar medium (ISM).
• Methylketene is energetically close to the global minimum trans-acrolein, making it a potential interstellar candidate, but it remains undetected despite searches.
• Understanding the potential energy surface and formation pathways of C3H4O isomers is crucial for identifying new molecules in space.

Purpose of the Study:

• To investigate the formation pathways of C3H4O isomers, focusing on methylketene and other potential interstellar candidates.
• To provide accurate spectral data for newly identified potential interstellar molecules to aid observational astronomers.
• To re-evaluate the presence and formation of methylketene in the interstellar medium.

Main Methods:

• High-level ab initio calculations using the CCSD(T)/cc-pVTZ method to determine the potential energy surface of C3H4O isomers.
• Detailed examination of reaction mechanisms and formation pathways for various C3H4O isomers.
• Computation of accurate spectral data for target molecules.

Main Results:

• Methylketene is found to be energetically favorable, only 1.9 kJ mol-1 above trans-acrolein, but its interstellar detection remains elusive.
• Gauche-propargyl alcohol and syn/anti-allenol are identified as promising new targets for interstellar observations, particularly in the TMC-1 region.
• Barrierless product channels involving OH radical support the candidacy of gauche-propargyl alcohol and allenols as interstellar species.

Conclusions:

• The study provides a more detailed interpretation of C3H4O formation mechanisms in the interstellar medium.
• Gauche-propargyl alcohol and allenols are proposed as viable candidates for future astronomical searches, supported by new spectral data.
• Further observational efforts are needed to confirm the presence of these molecules and resolve the C3H4O astrochemical conundrum.