The ring-collapse mechanism of C-24 (D-6d) has been analyzed using semiempirical AM1 and B3LYP/cc-pVDZ methods. Based on the ring-stacking/circumscribing model, two precursors are selected. Transition states and inter...
详细信息
The ring-collapse mechanism of C-24 (D-6d) has been analyzed using semiempirical AM1 and B3LYP/cc-pVDZ methods. Based on the ring-stacking/circumscribing model, two precursors are selected. Transition states and intermediates are located and energetics are computed. Before the stacking begins, the precursor and belt reach a suitable relative orientation accompanied by the release of a large amount of energy. It is observed that the reactions between the precursors and the belts are essentially endoergic in nature, whereas the reactions between the stable intermediates and the final belts are exoergic. The deformation energies (DE) and the bond lengths R of the precursors have been computed. The DE values suggest that there is a chance of the cleavage of the bicyclic precursors as the growth process proceeds toward the cage formation. In contrast, the monocyclic precursor is found to have lower deformation energies than the bicyclic precursor. Analysis of average bond length at different cages shows that a large window is formed and the system appears to follow a cascade-type bond formation. Comparisons are made to our previous results on C-28 growth. (c) 2005 Wiley Periodicals, Inc.
The unique properties of two classes of regular-hexagon-shaped benzenoid hydrocarbons are studied. The D-6h point group symmetry of the members of these series have made them natural objects of numerous past studies. ...
详细信息
The unique properties of two classes of regular-hexagon-shaped benzenoid hydrocarbons are studied. The D-6h point group symmetry of the members of these series have made them natural objects of numerous past studies. The D-6h total resonant sextet (TRS) one-isomer series among all benzenoid hydrocarbons of the same size has the maximum number of Clar resonant sextets, bay regions, and Kekue resonance structures. (C) 2002 Elsevier Science B.V. All rights reserved.
Reactions among the mono- to polycyclic carbon clusters have been analyzed using semiempirical AM1 and HF/6-31G* methods. The C-28 (D-2) fullerene cage has been considered. Various precursors are chosen with the appro...
详细信息
Reactions among the mono- to polycyclic carbon clusters have been analyzed using semiempirical AM1 and HF/6-31G* methods. The C-28 (D-2) fullerene cage has been considered. Various precursors are chosen with the appropriate carbon belts. It is observed that the reactions between the precursors and the belts are essentially endoergic in nature, whereas the reactions between the stable intermediates and the final belts are exoergic. Further, the second step of the process is really akin to an annealing mechanism. Also, it has been observed that, in the annealing process, a cascade type of bond-forming mechanism is in operation. (C) 2001 John Wiley & Sons, Inc.
暂无评论