Study On Monosaccharide Optimization And Coupling Reaction Mechanism Based On Quantum Chemistry

The development of chemistry into a basic discipline with solid theoretical system benefits from the proposal of theoretical chemistry,and the birth of theoretical chemistry benefits from the combination of physics and chemistry.As an inevitable product of the development of theoretical chemistry,computational chemistry has been gradually applied to explain experimental phenomena,elucidation of experimental principles,prediction of reaction difficulty and so on.With the rapid development of theoretical chemistry and computer,theoretical and computational chemistry has gradually become a unique branch with equal emphasis on experiment.Quantum chemistry,one of the most important theoretical chemistry,is now the mainstream theoretical calculation method,and is a basic science that applies the micro principles and micro methods of quantum mechanics to study chemical problems.At present,the mainstream of computational chemistry based on theoretical chemistry is to obtain the structural properties of molecules such as electronic properties and electromagnetic properties by using quantum chemistry software with effective mathematical approximations.This paper is based on the theoretical method of quantum chemistry to calculate the organic structure optimization and organic reaction mechanism.The basic content can be divided into the following parts:The first chapter introduces the basic theory and calculation method.In chapter two,the background knowledge of oligosaccharides reaction is introduced.The traditional B3LYP density functional method is used to optimize the intermediate,frequency and single point energy of three common pyranosaccharides(glucopyranose,mannopyranosyl and galactopyranose)in the corresponding solution.The free energy of solute in solvent environment is calculated by combining the formula to get the intermediate Stability.The stability of the intermediate is calculated to predict the difficulty of the reaction in the experiment,and then promote the synthesis of the experiment.The combination of experimental and computational results is not only helpful to the development of more effective glycoside bond synthesis,but also to the development of more stereoselective oligosaccharides.This work has been published as the first author on org.chem.front.2020,7,1606-1615.In chapter three,the background knowledge of coupling reaction is introduced.The micro mechanism of coupling reaction is studied in detail by using the classical B3LYP density functional method.The calculated coupling reaction system is Cu(I)catalyzed cross coupling reaction of(hetero)aryl halides to alkyl aryl ethers reported by Ma et al.The calculation results show that the micro reaction mechanism of the coupling reaction through four steps:(1)Oxidation addition;(2)Coordination effect;(3)Ligand exchange;(4)Reduction elimination.Tert-butoxide not only acts as a base,but also acts as a catalyst.According to the calculation results,the reaction path diagram and Gibbs free energy diagram are constructed.One of the intermediates is in good agreement with the intermediate shown in the experimental spectrum,which proves the rationality of the above mechanism.As the first author,this work of the mechanism calculation has been published in Acta chemica Sinica.The above work is to study the internal law of the system by using theoretical calculation method.In the case that the theoretical results are in good agreement with the experimental data and spectra,it also proves the feasibility of the theoretical and calculation methods in the study of reaction intermediates and reaction mechanism.The work of this paper is expected to provide theoretical support and guidance for the development of new glycosidic bonds and coupling reactions in sugar reactions and the development of new catalyst ligands.