Theoretical Study On Formation Of Heterocyclic Compounds And Dehydrogenation Of Ethanol

In recent years,with the continuous advancement of computer technology,chemists havegradually shifted from macroscopic phenomena to microscopic mechanisms,and the discipline of chemistry is no longer purely experimental science.The application of computational chemistry for theoretical simulations can help people obtain data that is difficult to obtain directly experimentally,and can also explain some experimental phenomena to optimize chemical reaction conditions.Based on the above ideas,this paper reveals the reaction mechanism of phosphine-catalyzed [3+3] cycloaddition reaction of azomethine imine with alkyne ketone and ethanol dehydrogenation on Co（111）surface.This paper discusses the reaction mechanism and dynamic conversion process of the above reactions.（1）PPh₃-catalyzed [3+3] cycloaddition reaction of but-3-yne-2-one with azomethine imine was investigated by density functional theory and Reax FF reaction field-molecular dynamics simulation.We have studied various possible reaction pathways.Density functional theory calculations indicate that the reaction is initiated by the nucleophilic attack of the catalyst PPh3 on but-3-yne-2-one to form intermediate 1,then intermediate 1 undergoes a proton transfer process,followed by nucleophilic addition reaction of intermediate 2 with azomethine imine to form intermediate 3.Next,intermediate 3 is subjected to intramolecular cycloaddition and the catalyst is removed to give the final product.The additive Ph OH plays an important role in the proton transfer process.It was finally determined that the C-C bond forming step was a stereoselective determining step,and the results showed that the product P（R）of the R configuration was the main product.（2）The VASP software based on the first-principles calculation method was used to study the decomposition and dehydrogenation of ethanol on Co（111）surface.The detailed reaction mechanism of ethanol dehydrogenation reaction was investigated,and three reactions of ethanol dehydrogenation were determined.The optimal adsorption sites for the reactants,transition states and products involved in the ethanol decomposition dehydrogenation on the Co（111）surface were determined.According to the calculation results,the adsorption of ethanol on the surface of cobalt is weakly adsorbed.Ethoxy,methine and C atoms are more likely to adsorb at the hcp sites,acetaldehyde is easily adsorbed at the bridge,and both methyland methane are preferably adsorbed to the top site of the surface by C atoms.The dehydrogenation reaction of ethanol on the surface of Co（111）studied can be carried out according to three paths: Path I is the stepwise dehydrogenation of ethanol to methane and carbon monoxide via intermediate acetaldehyde;Path II is the reaction between ethoxy and acetaldehyde produced by dehydrogenation of ethanol to finally form methane and carbon dioxide through the acetic acid;Path III is a process in which ethoxy and acetyl directly act to form ethyl acetate,and the Path I（CH₃CH₂OH→CH₃CH₂O→CH₃CHO→CH₃CO→CH₃+CO→ CH₂ → CH → CH₄+CO+C+H）is the optimal one.The dehydrogenation of ethoxyl to acetaldehyde in this reaction pathway is the rate-determining step,and the reaction energy barrier is 1.61 eV.