Theoretical Studies On Mechanisms Of Several Important Chemical Reactions And Solvent Effects

It is of great interest to investigate the chemical reaction and determine the reaction mechanism. Now we can theoretically study the chemical reaction process via combination of quantum chemical programs and the knowledge of chemistry. In order to match the practical system and obtain the reliable results, it is more and more attracting attention in theoretical and computational chemistry to evaluate the solvent effect on a reaction.In our work, the mechanisms of several important chemical reactions, related to the organic catalysis, photochemistry, and hydrolysis in biological system, have been theoretically investigated. Furthermore, the solvent effects of reactions have also been taken into account in our studies. In chapter 2, the mechanism of the GaCl3-catalyzed [4+1] cycloaddition ofα,β-unsaturated ketone with 2,6-dimethylphenyl isocyanide leading to unsaturatedγ-lactone derivative is reported. In this work, the function of GaCl3 promoter and its mechanism was clarified. It tured out that GaCl3 activator can be easily detached from the product, different from other promoters using transition metals.In addition, the self-consistent reaction field (SCRF) based on the polarized continuum model (PCM) was used to evaluate the solvent effect in toluene for the stationary points optimized at the B3LYP/6-31G* level. Our calculations indicated that the total reaction is stepwise and exothermic, and that the rate-limiting step is to overcome the barrier (9.36 kcal/mol) in the second step. Although the solvent effects increase the reaction barrier by about 5.0 kcal/mol, it has little influence on...