In this paper, we have disussed the internal rotation in sulfonylurea molecules,which belong to high active and low toxic herbicides and take the form of conformational iso-mers in their crystal structures. In order t...In this paper, we have disussed the internal rotation in sulfonylurea molecules,which belong to high active and low toxic herbicides and take the form of conformational iso-mers in their crystal structures. In order to understand the formation of their enantimers, weobtained a series of data of molecular energy of different conformation by using the molecularmechanics method and the stepwise rotation single-bond method. We found out the lowestinternal rotation passage and obtained the energy barrier of hindered rotation which is less 60kJ/mol. This result shows that there is a lower energy passage to exchange the conforma-tional isomers of these molecules, so exchanging the different conformational isomers is notvery difficult.展开更多
The conformations of the complexes which are formed in the interaction between chiral stationary phase(CSP) and diniconazole enantiomers have been optimized by molecular mechanics. Using molecular mechanics, we calcul...The conformations of the complexes which are formed in the interaction between chiral stationary phase(CSP) and diniconazole enantiomers have been optimized by molecular mechanics. Using molecular mechanics, we calculated the bond lengths, bond angles, dihedral angles and total energies of those complexes respectively. The results show that both R and S species of diniconazole can form complexes ( R CSP and S CSP) with chiral stationary phase by two hydrogen bonds. The hydrogen bonds of S CSP are stronger than those of R CSP. As compared with R CSP complex, S CSP complex is more stable, and has a longer retention time than R species in chiral separation. Based on the factor that there are high rotational barriers for the main single bonds in both R CSP and S CSP complexes, we can get the same conclusion as in experiments that the separation results have little changes with the temperature. The π π interaction between R or S species of diniconazole and CSP was not found.展开更多
A set of force field parameters for the radical cation of diazabicycle alkane are derived by "substracting" nonbonded molecular mechanics energies (MM2 method) from corresponding molecular orbital energies (...A set of force field parameters for the radical cation of diazabicycle alkane are derived by "substracting" nonbonded molecular mechanics energies (MM2 method) from corresponding molecular orbital energies (MNDO method) using a model compound containing the chemical structure to be parameterized. A general discussion of the N, N’ two-center three electrones bond in radical cations. The results are satisfactory.展开更多
文摘In this paper, we have disussed the internal rotation in sulfonylurea molecules,which belong to high active and low toxic herbicides and take the form of conformational iso-mers in their crystal structures. In order to understand the formation of their enantimers, weobtained a series of data of molecular energy of different conformation by using the molecularmechanics method and the stepwise rotation single-bond method. We found out the lowestinternal rotation passage and obtained the energy barrier of hindered rotation which is less 60kJ/mol. This result shows that there is a lower energy passage to exchange the conforma-tional isomers of these molecules, so exchanging the different conformational isomers is notvery difficult.
文摘The conformations of the complexes which are formed in the interaction between chiral stationary phase(CSP) and diniconazole enantiomers have been optimized by molecular mechanics. Using molecular mechanics, we calculated the bond lengths, bond angles, dihedral angles and total energies of those complexes respectively. The results show that both R and S species of diniconazole can form complexes ( R CSP and S CSP) with chiral stationary phase by two hydrogen bonds. The hydrogen bonds of S CSP are stronger than those of R CSP. As compared with R CSP complex, S CSP complex is more stable, and has a longer retention time than R species in chiral separation. Based on the factor that there are high rotational barriers for the main single bonds in both R CSP and S CSP complexes, we can get the same conclusion as in experiments that the separation results have little changes with the temperature. The π π interaction between R or S species of diniconazole and CSP was not found.
文摘A set of force field parameters for the radical cation of diazabicycle alkane are derived by "substracting" nonbonded molecular mechanics energies (MM2 method) from corresponding molecular orbital energies (MNDO method) using a model compound containing the chemical structure to be parameterized. A general discussion of the N, N’ two-center three electrones bond in radical cations. The results are satisfactory.
