This paper is one of a series of reports of theoretical researches on the mechanism of the Mannich reaction using the iminium salt as the potential Mannich reagent. According to the results of AM1 dynamic calcula...This paper is one of a series of reports of theoretical researches on the mechanism of the Mannich reaction using the iminium salt as the potential Mannich reagent. According to the results of AM1 dynamic calculations, the activation energies of key steps in conventional Mannich reactions between ammonia, formaldehyde and acetaldehyde in neutral and acidic media are 438 8 kJ/mol and 393 9 kJ/mol respectively. The activation energy of the rate controlling step of the Mannich reaction which contains the potential Mannich reagent is 274 7 kJ/mol. Therefore, it can be derived that the potential Mannich reagent can increase the rate of the reaction remarkably. The reasons for this have been discussed in terms of the orbital match and electrostatic interaction between the atoms of reactant complexes. In this paper another different conjectured mechanism of the potential Mannich reagent which can reduce the activation energy is considerably studied.展开更多
Molecular dynamics(MD) simulation of ethene diffusion in the lattice of HZSM 5 was performed at the temperature ranging from 300 K to 700 K. The calculated diffusion coefficients increase with the temperature from 2.6...Molecular dynamics(MD) simulation of ethene diffusion in the lattice of HZSM 5 was performed at the temperature ranging from 300 K to 700 K. The calculated diffusion coefficients increase with the temperature from 2.60×10 -9 m 2/s at 300 K to 12.78×10 -9 m 2/s at 700 K. The Arrhenius plot gives an activation energy of 6.31 kJ/mol . The anisotropy of the diffusion process was examined.展开更多
文摘This paper is one of a series of reports of theoretical researches on the mechanism of the Mannich reaction using the iminium salt as the potential Mannich reagent. According to the results of AM1 dynamic calculations, the activation energies of key steps in conventional Mannich reactions between ammonia, formaldehyde and acetaldehyde in neutral and acidic media are 438 8 kJ/mol and 393 9 kJ/mol respectively. The activation energy of the rate controlling step of the Mannich reaction which contains the potential Mannich reagent is 274 7 kJ/mol. Therefore, it can be derived that the potential Mannich reagent can increase the rate of the reaction remarkably. The reasons for this have been discussed in terms of the orbital match and electrostatic interaction between the atoms of reactant complexes. In this paper another different conjectured mechanism of the potential Mannich reagent which can reduce the activation energy is considerably studied.
基金Supported by the National Natural Science Foundation of China(No.2 97730 2 1) and the Provisional EducationalFoundation of Jiangsu(Granted:98KJB15 0 0 0 1)
文摘Molecular dynamics(MD) simulation of ethene diffusion in the lattice of HZSM 5 was performed at the temperature ranging from 300 K to 700 K. The calculated diffusion coefficients increase with the temperature from 2.60×10 -9 m 2/s at 300 K to 12.78×10 -9 m 2/s at 700 K. The Arrhenius plot gives an activation energy of 6.31 kJ/mol . The anisotropy of the diffusion process was examined.
