Systematic Investigation of the Role of the Epoxides as Substrates for CO2 Capture in the Cycloaddition Reaction Catalyzed by Ascorbic Acid

Abstract

This work establishes a comprehensive theoretical framework for synthesizing cyclic organic carbonates through the cycloaddition of carbon dioxide (CO2) to epoxides under mild pressure and temperature conditions. Using advanced computational techniques, the study examines the thermodynamic and kinetic aspects of the reaction, with a particular focus on epoxide substrates featuring diverse substituents. Detailed analysis reveals activation energy barriers and identifies the rate-determining step, offering crucial insights into the molecular processes governing the reaction. The investigation highlights the significant role of steric and electronic effects in influencing substrate reactivity. Monosubstituted epoxides display stronger steric correlations, while bulkier and disubstituted substrates deviate due to the interplay of steric hindrance and electronic factors such as electrophilicity and chemical hardness. Additionally, localized steric effects and substituent electronegativity emerge as key contributors to transition state stability, with halogenated substrates showcasing nuanced reactivity profiles. Despite these advancements, machine learning models applied in this study demonstrate poor predictive performance, underscoring the challenge of capturing the complex interplay of substrate properties using current descriptors. This highlights the limitations of substrate-based approaches in predicting reaction outcomes. These findings emphasize that catalytic design plays a more decisive role than substrate modification in determining reaction efficiency. This work calls for a systematic exploration of ascorbic acid-based catalyst modifications to optimize energy barriers and improve overall reaction performance, paving the way for rational catalyst design and predictive catalysis in CO₂ valorization