Base-catalyzed thiol-epoxy reactions: Energetic and kinetic evaluations.

The mechanism of the base-catalyzed thiol-epoxide stage of the thiol-ene/thiol-epoxide curing process was investigated using quantum chemical tools. This study searched for conventional tertiary amines with low to medium basicity as initiators to control reaction rates and tailor industrial applications. Challenges arise from the stronger basicity of initiators, leading to an uncontrollable and short curing application period.

Computational Study on Radical-Mediated Thiol-Epoxy Reactions.

Radical-mediated thiol-epoxy reactions were elucidated for analyzing the overlap problem of the thiol-ene/thiol-epoxy systems using computational approaches. Nine epoxy model molecules were evaluated to mimic the chemical structures and reactivity of some industrial epoxy molecules. Modeling reaction mechanisms was conducted through density functional theory (DFT) calculations using the M06-2X/6-31+G(d,p) level at 1.

Insight into the Thiol-yne Kinetics via a Computational Approach.

Thiol-yne reactions have drawn attention because of the click nature as well as the regular step-growth network nature of their products, despite the radical-mediated reactant. However, the factors governing the reaction pathways have not been examined using quantum chemical tools in a comprehensive manner. Thereupon, we have systematically investigated the mechanism of thiol-yne reactions, focusing on the structural influences of thiol and alkyne functionalities.

Solvent Effects on Thiol-Ene Kinetics and Reactivity of Carbon and Sulfur Radicals.

The thiol-ene reaction is one of the fundamental reactions in biochemistry and synthetic organic chemistry. In this study, the effect of polar media on the reaction kinetics is taken into account by using the transition state theory; the reactivities of the carbon and sulfur radicals have also been rationalized by using conceptual DFT. The results have shown that the solvents have more impact on hydrogen atom transfer reactions and the chain transfer rate constant, , can be increased by using nonpolar solvents, while propagation reactions are less sensitive to media.

Effect of Substituents on the Stability of Sulfur-Centered Radicals.

High-level ab initio calculations have been used to calculate the standard and inherent radical stabilities (RSEs) of a test set of 41 sulfur-centered radicals, chosen for their relevance in fields as diverse as combustion, atmospheric chemistry, polymer chemistry, and biochemistry. Radical stability was shown to be profoundly affected by substituents, varying over a 30 kcal mol(-1) range for the test set studied. Like carbon-centered radicals, substituent effects on sulfur-centered radical stabilities result from the competition between the stabilizing effect of electron delocalization by lone pair donation and π-acceptance, and the destabilizing effect of σ withdrawal.

Comparison of Thiyl, Alkoxyl, and Alkyl Radical Addition to Double Bonds: The Unusual Contrasting Behavior of Sulfur and Oxygen Radical Chemistry.

High-level ab initio calculations have been used to compare prototypical thiyl, alkoxyl, and alkyl radical addition reactions. Thiyl radical addition to the sulfur center of thioketones is exothermic and rapid, occurring with negative enthalpic barriers and only weakly positive Gibbs free energy barriers. In stark contrast, alkoxyl radical addition to the oxygen center of ketones is highly endothermic and occurs with very high reaction barriers, though these are also suppressed.