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Preliminary Free Energy Map of Prebiotic Compounds Formed from CO2, H2 and H2S
1Department of Chemistry & Biochemistry, University of San Diego, San Diego, CA 92110, USA.
Life (Basel, Switzerland)
|November 11, 2022
Summary
Sulfur-containing organic compounds (CHOS) can form in early Earth conditions. Thiols are favored, influencing prebiotic chemistry and the autocatalytic formose reaction.
Area of Science:
- Astrochemistry
- Prebiotic Chemistry
- Quantum Chemistry
Background:
- Understanding the origins of life requires identifying plausible prebiotic chemical pathways.
- The role of sulfur in prebiotic chemistry is less understood compared to oxygen-based compounds.
Purpose of the Study:
- To investigate the formation of carbon-hydrogen-oxygen-sulfur (CHOS) compounds under prebiotic conditions.
- To determine the influence of hydrogen sulfide (H2S) on the thermodynamic stability of CHOS species.
- To explore the implications for sulfur-containing analogs of the formose reaction.
Main Methods:
- Utilized first-principles quantum chemistry to calculate free energies of CHOS compounds in aqueous solution.
- Generated a thermodynamic map of one- and two-carbon CHOS species.
- Analyzed the role of mercaptoacetaldehyde in sulfur-containing formose reaction analogs.
Main Results:
- Thermodynamically favored the formation of thiols over thioesters, thioacids, and thiones.
- Identified mercaptoacetaldehyde as a key intermediate in sulfur-analogous prebiotic reactions.
- Demonstrated that the thiol group can introduce asymmetry and thermodynamic selectivity.
Conclusions:
- Sulfur incorporation into prebiotic organic molecules is thermodynamically feasible, favoring thiol formation.
- Mercaptoacetaldehyde plays a crucial role in sulfur-modified prebiotic reaction networks.
- Sulfur's presence can lead to selective formation of specific organic compounds, impacting origin-of-life scenarios.
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