Cyclic Orbital Interaction and Orbital Phase in Acyclic Conjugation

Inagaki, Satoshi; Kawata, Hirofumi; Hirabayashi, Yoshio

doi:10.1246/bcsj.55.3724

Cited by 34 publications

(23 citation statements)

References 120 publications

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“…The delocalization of six p electrons in the four p-orbitals of the linear conjugation is disfavored by the orbital phase discontinuity 306 S. Inagaki (Sects. 2.1 and 3.1 in Chapter "A Orbital Phase Theory" by Inagaki in this volume) [98,99]. The n-p conjugation is weaker relative to that in 12 where a similar phase restriction is absent.…”

Section: Triazene Hn=nnh 2 and 2-tetrazene H 2 Nn=nnhmentioning

confidence: 90%

Orbitals in Inorganic Chemistry: Metal Rings and Clusters, Hydronitrogens, and Heterocyles

Inagaki

2009

Topics in Current Chemistry

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A chemical orbital theory is useful in inorganic chemistry. Some applications are described for understanding and designing of inorganic molecules. Among the topics included are: (1) valence electron rules to predict stabilities of three- and four-membered ring metals and for those of regular octahedral M(6) metal clusters solely by counting the number of valence electrons; (2) pentagon stability (stability of five- relative to six-membered rings in some classes of molecules), predicted and applied for understanding and designing saturated molecules of group XV elements; (3) properties of unsaturated hydronitrogens N( m )H( n ) in contrast to those of hydrocarbons C( m )H( n ); (4) unusually short nonbonded distances between metal atoms in cyclic molecules.

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Section: Triazene Hn=nnh 2 and 2-tetrazene H 2 Nn=nnhmentioning

confidence: 90%

Orbitals in Inorganic Chemistry: Metal Rings and Clusters, Hydronitrogens, and Heterocyles

Inagaki

2009

Topics in Current Chemistry

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“…The electron delocalizations in the linear and cross-conjugated hexatrienes serve as good models to show cyclic orbital interaction in non-cyclic conjugation (Schemes 2 and 3), to derive the orbital phase continuity conditions (Scheme 4), and to understand the relative stabilities (Scheme 5) [15]. (ii) The electron donating and accepting orbitals are in phase.…”

Section: Non-cyclic Conjugationmentioning

confidence: 99%

“…Trimethylenemethane (TMM) and 2-buten-1,4-diyl (BD) dianions (Scheme 6a, b) are chosen as models for linear and cross-conjugated dianions. The bond polarization (Scheme 7) is shown to contain cyclic orbital interaction (Scheme 6c) even in non-cyclic conjugation [15]. The orbital phase continuity-discontinuity properties (Scheme 6d, e) control the relative thermodynamic stabilities.…”

Section: Polarization Of Bondsmentioning

confidence: 99%

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An Orbital Phase Theory

Inagaki

2009

Orbitals in Chemistry

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Cyclic orbital interactions are contained in non-cyclic conjugation as well as cyclic conjugation. For effective interactions, the orbitals are required to meet simultaneously the phase continuity conditions: (1) out of phase relation between electron-donating orbitals; (2) in phase relation between electron-accepting orbitals and between electron-donating and -accepting orbitals. The orbital phase theory is applicable to diverse chemical phenomena of non-cyclic conjugate systems, e.g., relative stabilities of non-cyclic isomers, and selectivities of the reactions through non-cyclic transition structures. The orbital phase theory also includes the rules for cyclic systems, i.e., the Wooward-Hoffmann rule for stereoselection of organic reactions and the Hueckel 4n + 2p electron rule for aromatic molecules. Derivation and applications of the orbital phase theory are reviewed.

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“…Later, more sophisticated approaches to analysis of p-electron energies of polyenelike systems have been suggested, e.g. those based on perturbative treatments of configuration interaction (CI) [24,25] (besides, the second energy expansion was asserted to converge [25] even in the case of uniform resonance parameters). Since the authors of these studies ultimately abandon many-electron wave functions and turn to interacting atomic or bond orbitals (AOs or BOs) when looking for chemically illustrative pictures of conjugation (delocalization) effects, the methods concerned may be regarded (and referred to) as indirect ones.…”

Section: Introductionmentioning

confidence: 99%

A simple rationale for lowered stabilities of branched and cross-conjugated polyenes

Gineitytė

2016

Monatsh Chem

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The study is aimed at revealing the decisive factors for relative stabilities of acyclic p-electron systems of polyenes, the carbon backbones of which are of different type of branching. The systems are modeled as sets of N weakly interacting double (C=C) bonds. The relevant total p-electron energies are represented in the form of power series containing members of even orders with respect to the averaged resonance parameter of single (C-C) bonds. For distinct isomers of the same polyene, both zero-order energies and respective second-order corrections are shown to take uniform values. Relative stabilities of these isomers are then primarily determined by the fourth-order member of the series that, in turn, consists of two additive components of opposite signs, viz., of the stabilizing component expressible as a sum of transferable increments of individual triplets of linearly conjugated C=C bonds [i.e., of the three-membered conjugated paths (CPs)] and of the destabilizing component depending on overall adjacencies (connectivity) of C=C bonds. Lower stabilities of p-electron systems of branched and/or crossconjugated polyenes vs. the linear ones then follow from comparative analyses of the relevant fourth-order energies, and this destabilization is shown to originate either from (a) a reduced number of CPs or from (b) higher adjacencies of C=C bonds in the former isomers. An actual interplay of both factors (c) also is rather common. The three cases (a)-(c) are illustrated by specific examples. Graphical abstract

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Cyclic Orbital Interaction and Orbital Phase in Acyclic Conjugation

Abstract: The orbital phase continuity-discontinuity property is shown to control electron delocalization and polarization even in open chain conjugated molecules. Its chemical consequences are discussed.

Cited by 34 publications

References 120 publications

Orbitals in Inorganic Chemistry: Metal Rings and Clusters, Hydronitrogens, and Heterocyles

Orbitals in Inorganic Chemistry: Metal Rings and Clusters, Hydronitrogens, and Heterocyles

An Orbital Phase Theory

A simple rationale for lowered stabilities of branched and cross-conjugated polyenes

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