Study On Reaction Mechanism And Dynamics Of The Difluoroethylamine Synthesis

This thesis focuses on the in-depth study of the synthesis reaction of difluoroethylamine.The main research contents are:?1?the reaction mechanism and kinetics of NH₃substituted C₂H₃F₂Cl,?2?the substitution reaction of NH₃with C₂H₃F₂X?X=Cl,Br And I?Comprehensive analysis and research,?3?Impact of organic solvents on the reaction process.Based on literature reports and surface potential analysis,four possible reaction paths were identified.First,the B3LYP/6-31++G calculation method in the gussian software was used to complete the transition state search and molecular structure optimization and transition state structure confirming of the four mechanisms.Secondly,based on the potential energy surface relationship on the reaction mechanism,molecular frontier orbital analysis and natural bond orbital analysis were used to verify the correctness of the reaction mechanism.eventually,the optimal reaction mechanism was determined to be the ammonia molecular back attach substitution mechanism.Finally,based on the optimal mechanism,the natural charge analysis was used to analyze the possible complex structure of the substituent attack and leaving group leaving process.The analysis determined that there are 5 possible complexes in the reaction process and these molecular structure is optimized.The precursor dipole-dipole complexes that exist during the offensive substitution of carbon atoms by ammonia molecules have been determined to be complx-a,which is the N and H atoms in NH₃ are closes interact with H and F atoms;the subsequent ion-dipole complexes present in the leaving process are complx-d and complx-e,that is,the chlorine atom interacts with any H atom to form a complex.Using the Kisthelp software to study the kinetic characteristics of NH₃ substituted C₂H₃F₂Cl shows that kinetic equation is:.According to the reaction potential energy surface,rate constant and equilibrium constant,the three synthetic processes of NH₃ substituted C₂H₃F₂X?X=Cl,Br and I?are comprehensively analyzed.The research shows that the C₂H₃F₂Cl reaction has the highest equilibrium constant and signif-icant difference from the other two reactions,which means the conversion rate is the highest,and the other analysis have no obvious difference,finally,the study demonstate that NH₃ substituted C₂H₃F₂Cl reaction has great advantage.The CPCM solvent calculation model was used to study the solvent effects of the addition of six organic solvents and aqueous solutions such as DMF,DMSOand CCl4.The results showed that the addition of organic solvents can increase the energy of the complex and reduce the the energy of transition state and intermediate.The relationship between surface energy and structural analysis show that the stronger the polarity of the solvent,the lower the C-X bond length and the C-N bond length.In-depth analysis found that the relationship between the degree of charge heterogeneity and the transition state C-X bond and C-N bond length is analyzed.The research shows that the higher the value of the charge heterogeneity,the shorter the C-X bond and the longer the C-N bond.The C-X bond length the stronger the polarity,the higher the degree of charge heterogeneity,leading to the growth of the transition state C-N bonds and the shortening of the C-X bonds,which in turn would reduce the transition state activation energy.