Moebius-Hueckel concept in organic chemistry. Application of organic molecules and reactions

Zimmerman, Howard E.

doi:10.1021/ar50044a002

Cited by 507 publications

(312 citation statements)

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“…83 Thus, all pericyclic reactions proved to be aromaticity-controlled reactions. The law of orbital symmetry 88 and frontier orbital theory 89 lead to the same regioselectivity of pericyclic reactions. Electrocyclic reactions as shown in Figure 16 must proceed thermally and photochemically by way of Hückel-and Möbius-type transition states, respectively.…”

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confidence: 95%

Graph Theory of Aromatic Stabilization

Aihara¹

2016

BCSJ

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Aromaticity is very sensitive to the geometry of the π-system. Topological resonance energy (TRE), defined graphtheoretically, represents an aromatic stabilization energy (ASE) arising from cyclic conjugation in the π-system. TRE can be calculated for not only ground-state but also excited-state species. The TRE concept has since been extended analytically to solve many different problems concerning aromaticity and reactivity. Bond resonance energy (BRE), defined in harmony with TRE, is an excellent probe for exploring kinetic stability of cyclic π-systems. It represents the contribution of individual π-bonds to global aromaticity. The well-known isolated pentagon rule (IPR) for fullerenes was verified in terms of BRE. Superaromatic stabilization energy (SSE) defined for macrocyclic π-systems finally confirmed the absence of macrocyclic aromaticity in kekulene. A novel local aromaticity index for polycyclic aromatic hydrocarbons (PAHs) was devised by reinterpreting the definition of SSE. We then found that aromatic properties of some PAHs are not compatible with Clar's aromatic sextet rule. We now feel that many fundamental problems with regard to aromatic stabilization and related phenomena have been solved conceptually.

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confidence: 95%

Graph Theory of Aromatic Stabilization

Aihara¹

2016

BCSJ

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“…Nevertheless, there is the criticism that FO theory cannot explain how molecular orbitals transform from the reactants to products except for the frontier orbitals. 50 The WÀH's correlation diagram method is not as widely applicable as other methods, such as the FO method 1,2 or M€ obiusÀHückel method, 51 as Smith and March have pointed out. 52 This limitation is well illustrated by the fact that only a limited number of diagrams that are consistent with both FO theory and the experimental results have been drawn so far, even though correlation diagrams are the foundation of WÀH theory.…”

Section: Resultsmentioning

confidence: 99%

Quantization of Chemical Reaction: The Dynamic Correlation Diagram Method Free From Noncrossing Rule

Nohira

2012

J. Theor. Comput. Chem.

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Both Fukui's frontier orbital (FO) theory and WoodwardÀHoffmann's orbital symmetry conservation (WÀH) theory are based on the molecular orbital theory. However, there are some obvious inconsistencies between the two theories in explaining the electron movement. The process of chemical reactions has been explained by the potential surface analysis based on the time-independent Schr€ odinger equation. However, this approach is not always appropriate for describing unsteady states, because the variable of reaction coordinate should be time t by its very nature. When considering the time-scale of chemical reactions for molecules, there is inherent uncertainty in the energy levels for the midway state of chemical reactions owing to the Heisenberg uncertainty principle. The states which can be accurately described by quantum mechanics exist discontinuously in chemical reactions. Such quantization of chemical reactions solves all noncrossing problems. We also show that such an essential fact leads to new concepts and theories in chemical reactions such as stable molecule, elementary reaction and minimum deformation of orbital phases. Finally, taking the regularity in organic reactions as an example, we demonstrate that FO theory and WÀH theory can be unified consistently by the universally applicable \dynamic correlation diagram method."

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“…In the weighted adjacency matrix A 0 , all edges crossing the 'seam' of the Mö bius band carry a factor of À1 to take account of the effect of the twist on the overlap of neighbouring p p orbitals (Fig. 3) [21,22]. Eigenvalue spectra of Möbius r and p systems are thus in general different.…”

Section: Resultsmentioning

confidence: 99%