A computational analysis of solvent effect :|thiol-ene reactions and CaO bond strength within hydrated calcium clusters

Abstract

In the first part this thesis, the solvent effect on thiol-ene reaction kinetics is elucidated. 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, kCT , can be increased by using non-polar solvents, while propagation reactions are less sensitive to media. Similarly, the kP /kCT ratio can be manipulated by changing the environment in order to obtain tailor-made polymers. Regarding the DFT descriptors, the local and global electrophilicity indices are well correlated with the propagation rate constant kP , whereas global electrophilicty index is associated with the chain transfer rate constant kCT . Overall, electrophilicy indices can be used with confidence to predict the kinetics of thiol-ene reactions. In the second part, the solvent effect on hydrated calcium clusters are investi gated. Calcium ions have significant role on biochemical processes, which makes the enlightenment of hydration of calcium ion crucial. The most stable form of calcium clusters is determined by using vibrational spectroscopy. DFT is used for structural optimizations and local mode analysis (LMA) is utilized in order to obtain the force constants of Ca-O bonds in vacuum and water environment. Bond strength orders are calculated for each bond, and it is concluded that CN of 6 is preferred in aqueous solutions, whereas the bonds get weaker as the cluster size increases in gas phase.