The ab initio calculations were performed at the RHF/4-31G level with the reaction pathways of the iso-merization and dehydrogenation of methylnitrene by the intrinsic reaction coordinate method. The results show that...The ab initio calculations were performed at the RHF/4-31G level with the reaction pathways of the iso-merization and dehydrogenation of methylnitrene by the intrinsic reaction coordinate method. The results show that the transformation from methylnitrene to methylenimine would be very easy. This accountes for the experimental fact that one couldn' t find the methylnitrene, but only obtained the methylenimine in the pyrolysis of methyl azide. The mode-selective study reveals the reaction coordinates (IRC) of isomerization and dehydrogenation of methylnitrene are associated with the molecular deformation mode of 1191 cm-1 and the methyl group unsymmetrical stretch mode, respectively. The coupling between normal coordinates is favourable to select the reaction channel of isomerization.展开更多
The tautomerism of formamide has been investigated by ab initio calculation using RHF/4-31G basis set. The change in some physical properties along the reaction path is presented. In the study of molecular reaction ki...The tautomerism of formamide has been investigated by ab initio calculation using RHF/4-31G basis set. The change in some physical properties along the reaction path is presented. In the study of molecular reaction kinetics, we have calculated all the kinetic parameters according to statistical thermodynamics and transition state theory. The combination of kinetics analysis with IRC analysis has indicated that the tautomerism is concerted but the geometric changes are nonsynchronous; the lifetime of the transition state is short and the transition state is tight type; the formamide is more stable than formimidic acid; the kinetic rate constant of backward reaction is larger than that of the forward reaction in the range of temperature studied.展开更多
The ab initio calculations were performed by the intrinsic reaction coordinated(IRC) method for the reaction paths of the dehydrogenations of methylenimine. We determined the geometries and energies of the transition ...The ab initio calculations were performed by the intrinsic reaction coordinated(IRC) method for the reaction paths of the dehydrogenations of methylenimine. We determined the geometries and energies of the transition states and obtained the activation energies, activation entropies and the statistical A factors on the RHF/4 -31G singlet potential energy surface. The mode selective study reveals the intrinsic reaction coordi-nates(URC) of 1 ,1 and 1 ,2 dehydrogenations of methylenimine to be related with the H2C= group symmetrical stretch mode and the =NH group stretch mode, respectively. The vibration coupling between the normal coordinates occurs in either of these two reaction paths.展开更多
基金This work was supported by the State Natural Science Foundation of China
文摘The ab initio calculations were performed at the RHF/4-31G level with the reaction pathways of the iso-merization and dehydrogenation of methylnitrene by the intrinsic reaction coordinate method. The results show that the transformation from methylnitrene to methylenimine would be very easy. This accountes for the experimental fact that one couldn' t find the methylnitrene, but only obtained the methylenimine in the pyrolysis of methyl azide. The mode-selective study reveals the reaction coordinates (IRC) of isomerization and dehydrogenation of methylnitrene are associated with the molecular deformation mode of 1191 cm-1 and the methyl group unsymmetrical stretch mode, respectively. The coupling between normal coordinates is favourable to select the reaction channel of isomerization.
文摘The tautomerism of formamide has been investigated by ab initio calculation using RHF/4-31G basis set. The change in some physical properties along the reaction path is presented. In the study of molecular reaction kinetics, we have calculated all the kinetic parameters according to statistical thermodynamics and transition state theory. The combination of kinetics analysis with IRC analysis has indicated that the tautomerism is concerted but the geometric changes are nonsynchronous; the lifetime of the transition state is short and the transition state is tight type; the formamide is more stable than formimidic acid; the kinetic rate constant of backward reaction is larger than that of the forward reaction in the range of temperature studied.
文摘The ab initio calculations were performed by the intrinsic reaction coordinated(IRC) method for the reaction paths of the dehydrogenations of methylenimine. We determined the geometries and energies of the transition states and obtained the activation energies, activation entropies and the statistical A factors on the RHF/4 -31G singlet potential energy surface. The mode selective study reveals the intrinsic reaction coordi-nates(URC) of 1 ,1 and 1 ,2 dehydrogenations of methylenimine to be related with the H2C= group symmetrical stretch mode and the =NH group stretch mode, respectively. The vibration coupling between the normal coordinates occurs in either of these two reaction paths.
