Bicycloaromaticity.  4m + 2, 4n rule

Goldstein, M. J.

doi:10.1021/ja01000a069

Cited by 70 publications

(22 citation statements)

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“…The "hyperconjugation" of various sorts is explained in the same manner. The stabilization due to homo-aromaticity or bicycloaromaticity of Goldstein (57), the stability in spirocycles, pericycles (58), "laticycles," and "longicycles" of Goldstein and Hoffmann (59), that of spirarenes of Hoffmann et al (60), and so on, are all understood as examples of the stabilization due to the delocalization between HOMO and LUMO, although other explanations may also be possible.…”

Section: Talsmentioning

confidence: 99%

Role of Frontier Orbitals in Chemical Reactions

Fukui

1982

Science

2,239

817

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Section: Talsmentioning

confidence: 99%

Role of Frontier Orbitals in Chemical Reactions

Fukui

1982

Science

2,239

817

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“…Recent years have witnessed the coining of such operational terms as homoconjugation 72 and bicycloconjugation 73 for the purpose of denoting interaction between two or more formally isolated π functions. Of course, the effects of π delocalization here are significantly less pronounced and thus more difficult to discern than those arising from the direct, uninterrupted, process.…”

Section: Scheme 11mentioning

confidence: 99%

Synthesis and Study of Select Heterocycles

ANASTASSIOU¹

1975

The Chemistry of Nonbenzenoid Aromatic Compounds –II

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The central theme of this review is the synthesis and subsequent study of a variety of π heterocycles with particular emphasis placed on the recognition of key steric and electronic factors controlling the development of heteroaromaticity as well as its less conventional variants, heterohomoaromaticity and heterobicycloaromaticity. The first three sections are devoted to the hetero[9]annulenes, their benzologues and the hetero[13]annulenes respectively and incorporate information attesting to the validity of Hückel's 4n + 2 rule in spite of frequent need for rather major, potentially damaging, skeletal readjustments. In each case, there is also unmistakable indication of an inverse relationship between heteroatom electronegativity and the development of 'aromatic' character. Section D contains information establishing the existence of bicycloconjugation in the 9-heterobicyclo[4.2.1]nona-2,4,7-triene system. Lastly, section E deals with the 2-heterobicyclo[3.2.1]octa-3,6-diene skeleton, incorporating data which are indicative of the system's ability to realize a homoconjugated frame.

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“…To prove these predictions we have to determine the symmetry species of those states \{IJ (see (1)) of the radical cations l(nt (assumed symmetry C2Y) which correspond to the PE bands CD and ® (Table I). These assignments, which will be described for 1(1), 1(3) and 1(4) in detail in subsequent contributions [18,19,23] have been carried out by the method outlined in the previous chapter, using the "bicyclo aromatic" compounds [24] 3,5 and 6 as reference systems. (Preliminary communications: [7,20]).…”

Section: (N)mentioning

confidence: 99%

Photoelectron‐Spectroscopic Assignment of Symmetry Species to the Lower Electronic States of Unsaturated Hydrocarbon Radical Cations

Heilbronner

1972

Israel Journal of Chemistry

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The competitive through-space and through-bond interaction of two symmetry-equivalent, semi-localized orbitals 'Pa, 'Pb (= 7T or lone-pair orbitals) in a molecule M of C s or higher symmetry can lead either to the natural order of the corresponding de localized orbitals, i.e., IjJ _ ':::::-('Pa -'Pb)/.j2 above 1jJ+ ' :::::-('Pa + 'Pb)/.,jI, or to the inverted order, i.e., IjJ + above IjJ _. It is shown that one can discriminate between these two situations through an analysis of the PE spectrum of a molecule M' which differs from M only by an additional semi-localized orbital 'Pc of known symmetry behaviour. The method is exemplified by an investigation of the dependence of the 7T-orbital sequence in 3,6-bridged 1,4cyclohexadienes on the dihedral angle between the two C-CH=CH-C moieties.Photoejection of an electron e" from a neutral, closed shell molecule M leads, according toto a radical cation M+ in the electronic state 'l1J =(1/10)2 (1/1,)2 (1/12)2 •.• (1/1 J)' ... (I/IN)2. This state belongs to the same symmetry species ( = irreducible representation) of the symmetry group of M as the vacated orbital 1/1J = };IlCJIleJ>W The current interest in molecular oribtals as qualitative (or semi-quantitative) model concepts for the rationalisation and prediction of chemical properties (e.g., [2]) has had a strong influence on the rapid development of photo-electron spectroscopy ( =PE spectroscopy). The reason is that this technique [3] yields information about orbital characteristics which are otherwise difficult, if not impossible, to obtain. Typical examples are a) orbital energies eJ = e(1/1 J ), which can be measured under the implicit assumption of the validity of Koopmans' theorem [4] , b) the relative locations of the nodes in the vacated orbital 1/ 1 J, which can be inferred in some cases from an analysis of the vibrational pattern of the corresponding PE bands [3,5],or c) the absolute value IcJp I of the coefficient of an atomic p orbital eJ>p centered at a heavy atom, which can be determined under favorable conditions (e.g., linear molecule * Part 33 of: Applications of photoelectron-spectroscopy; for part 32, see Ref. I. 143 144 E. HEILBRONNER lsr. J. Chem.,

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Bicycloaromaticity. 4m + 2, 4n rule

Cited by 70 publications

References 0 publications

Role of Frontier Orbitals in Chemical Reactions

Role of Frontier Orbitals in Chemical Reactions

Synthesis and Study of Select Heterocycles

Photoelectron‐Spectroscopic Assignment of Symmetry Species to the Lower Electronic States of Unsaturated Hydrocarbon Radical Cations

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