Investigating the Photolysis Mechanism of Propylene Oxide Using DFT and TD-DFT

Area of Science:

• Astrochemistry
• Physical Chemistry
• Quantum Chemistry

Background:

• Propylene oxide (PO) is a chiral molecule detected in interstellar space.
• Understanding PO's interstellar homochirality is key to the cosmic origins of life.
• Previous studies show 185 nm photolysis yields propanal and acetone.

Purpose of the Study:

• To investigate detailed photolysis mechanisms of propylene oxide (PO).
• To elucidate the role of excited states and diradical pathways in PO photolysis.
• To provide insights into the origins of PO homochirality in space.

Main Methods:

• Density Functional Theory (DFT) calculations.
• Time-dependent DFT (TD-DFT) for excited states.
• Analysis of potential energy surfaces and reaction pathways.

Main Results:

• PO photolysis proceeds via diradical pathways, consistent with prior proposals.
• Excited state pathways are more favorable than ground state pathways for 185 nm photolysis.
• Potential energy surfaces suggest preferential formation of propanal.

Conclusions:

• This study clarifies PO photolysis mechanisms, supporting diradical pathways.
• Photolysis via excited states is crucial, overcoming high ground-state activation energies.
• Findings offer insights into interstellar PO homochirality and the origins of life.