Insight into the Thiol-yne Kinetics via a Computational Approach

Area of Science:

• Polymer Chemistry
• Organic Chemistry
• Computational Chemistry

Background:

• Thiol-yne reactions are valuable due to their click chemistry nature and step-growth polymerization capabilities.
• The mechanistic factors influencing thiol-yne reaction pathways, particularly under radical conditions, require comprehensive investigation.
• Existing studies lack detailed quantum chemical analysis of structural effects on thiol-yne reaction mechanisms.

Purpose of the Study:

• To systematically investigate the mechanism of thiol-yne reactions using quantum chemical tools.
• To elucidate the influence of thiol and alkyne structural features on reaction pathways.
• To understand the factors governing reaction kinetics and E/Z diastereoselectivity in thiol-yne polymerization.

Main Methods:

• Density functional theory (DFT) was employed to model 11 diverse thiol-yne reactions.
• A benchmark study identified M06-2X/6-31+G(d,p) as a cost-effective computational methodology.
• Analysis focused on reaction kinetics, structure-reactivity relationships, and diastereoselectivity.

Main Results:

• Spin density and the stability of sulfur radicals (propagation) and alkenyl intermediates (chain transfer) are key determinants of reaction rates.
• Intramolecular π-π stacking interactions at transition states were identified as the cause of Z-diastereoselectivity.
• The study provides insights into the first cycle of thiol-yne polymerization.

Conclusions:

• Quantum chemical calculations offer a powerful approach to understanding complex reaction mechanisms like thiol-yne reactions.
• Structural factors of thiols and alkynes significantly impact reaction kinetics and product stereochemistry.
• This work provides a foundation for designing and controlling thiol-yne reactions for specific applications.