摘要:

AbstractThe synthesis and aromaticity of 1,6‐methano[10]annulene and its analogues containing a heteroatom bridge suggested the possibility that the homologous series of bridged [4n+ 2]annulenes1, 2, 3, etc., formally derived from the acene series, could be developed. In the pursuit of this concept a set of systematically bent bridged [14]annulenes which permitted a scrutinization of the steric prerequisite of the Hückel rule — the requirement of a planar ring skeleton — were built up. Moreover, a new synthetic strategy based on the synthon cycloheptatriene‐1,6‐dicarboxaldehyde has provided access to the two next higher homologues (syn‐series) of 1,6‐methano[10]annulene, i.e., syn‐1,6:8,13‐bismethano[14]annulene and syn, syn‐1,6:8,17:10,15‐trismethano[18]

ISSN:0021-2148    

DOI:10.1002/ijch.198000075

出版商:WILEY‐VCH Verlag    

年代:1980

数据来源: WILEY

摘要:

Abstract1,5,9‐Cyclododecatriyne has been synthesized by a bromination‐dehydrobromination sequence starting fromall‐cis‐1,5,9‐cyclododecatriene. Its physical properties point to substantial interaction of the acetylenic groups through space and through bond although this effect does not result in significant homoaromatic stabilization. Attempts to convert the triyne to isolable 1,2:3,4:S,6‐tricyclobutabenzene failed, but condensed phase thermolysis in the presence of dimethylmaleate led to the isolation of a formal triadduct. Flash pyrolysis resulted in the formation of hexaradialene. The latter is an extremely air sensitive, polymerizable molecule, devoid of detectable aromatic stabilization, in accord with theoretical treatments. Thermochemical estimates are presented which indicate the exothermicity of the 1,5,9‐cyclododecatriyne → hexaradialene interconversion. The most likely intermediate in this transformation is 1,2:3,4:5,6‐tricyclobutabenzene, also in accord with group equivalent calculations, although other pathways cannot be.rul

ISSN:0021-2148    

DOI:10.1002/ijch.198000076

出版商:WILEY‐VCH Verlag    

年代:1980

数据来源: WILEY

ISSN:0021-2148    

DOI:10.1002/ijch.198000077

出版商:WILEY‐VCH Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractRadical anions of 10,15‐dimethyl‐2,4,11,13‐tetrakisdehydro[18]annulene‐1,6‐dione (syn‐18), 6,15‐dimethyl‐2,4,11,13‐tetrakisdehydro[18]annulene‐1,10‐dione (anti‐18) and 8,13‐dimethyl‐2,9,11‐trisdehydro[16]annulene‐1,4‐dione (syn‐16) have been investigated by ESR and, in part, by ENDOR spectroscopy. The hyperfine patterns of these radical anions depend on the rate of intramolecular interconversion between two equivalent ion pairs in which the counterion is associated with one oxygen atom. It is found that the polarity of the solvent, which is an important factor influencing such a rate, does not affect the spectra of syn‐16⊕. quite in the same way as those of syn‐18⊕. and anti‐16⊕. This behavior, together with the lower stability of the former radical anion as compared to the two latter ones, points to substantial differences in physico‐chemical properties. Simple MO models indicate that the electronic structures of syn‐16⊕., syn‐18⊕. and anti‐16⊕. can be related to those of the corresponding 16π‐ and 18π‐perimeters. One is thus tempted to interpret the observed differenc

ISSN:0021-2148    

DOI:10.1002/ijch.198000078

出版商:WILEY‐VCH Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractThe perturbational molecular orbital theory by Haddon suggested the interesting possibility that introduction of homoconjugate linkages as a perturbation of the parent phenalenyl systems at 1,2‐, 1,10‐, and 10,11‐positions leads to the most unfavorable, medium, and most favorable energy changes, respectively. In order to prove this prediction, formation of 1,2‐, 1,10‐, and 10,11‐homophenalenyl systems were examined by employing the possible precursors such as the ketone5,29, the alcohol8, as well as the hydrocarbons16, 22, and37. In contrast to the prediction by PMO theory, these systems have no homoaromatic stabilization even in the 10,11‐homophenalenyl cation and anion. In further extension of this study, the synthesis of the hitherto unknown parent 8,16‐methano[2.2]metacyclophane‐1,9‐diene45has bee

ISSN:0021-2148    

DOI:10.1002/ijch.198000079

出版商:WILEY‐VCH Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractThe use of the perimeter model for the interpretation of magnetic circular dichroism of aromatic molecules is briefly reviewed. The model is applied to a rather difficult case, aceheptylene, whose electronic states are only distantly related to those of its perimeter. Correct signs are still predicted for the effects of magneticL1–L2andB1‐B2mix

ISSN:0021-2148    

DOI:10.1002/ijch.198000080

出版商:WILEY‐VCH Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractThe graph‐theoretical backbone of the topological resonance energy (TRE) concept is outlined and the connection with the Dewar resonance energy (DRE) approach is described. It appears that the TRE is not a new aromaticity index, but an optimal DRE‐like quantity of great practical value for understanding and predicting the aromatic stability of conjugated structures. In the TRE concept the most important result is the introduction of the acyclic polynomial which closely approximates the acyclic‐polyene reference structure. The rules for the construction of the acyclic (reference) polynomial are presented. Application of TRE to monocyclic systems, to polycyclic molecules and their radicals and ions, to homoaromatic systems, and to excited states is discussed. In most cases the agreement between the theory and experimental findings is good. However, in some examples the predictions appear to be inconsistent with reported data. The reasons for the occasional anomalies in the TRE are investigated. In addition, the problem of normalization of the TRE is consi

ISSN:0021-2148    

DOI:10.1002/ijch.198000081

出版商:WILEY‐VCH Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractStudies of structure‐resonance theory applied to π‐hydrocarbon systems are reviewed. The theory leads to quickly obtainable quantitative predictions of bond orders, charge distributions, and relative stabilities of ground state species or reaction intermediates. Numerical results correlate precisely with experimental properties, and with results of LCAO‐MO‐SCF calc

ISSN:0021-2148    

DOI:10.1002/ijch.198000082

出版商:WILEY‐VCH Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractStructure‐resonance theory is applied to transition metal π ligand complexes. This theory leads to specific, quantitative predictions of bond orders, charge distributions in ions, and relative stabilities of ground state species or reaction intermediates. In applications to hydrocarbon systems, numerical results correlate precisely with experimental properties, and with results of LCAO‐MO‐SCF calculations. Initial extensions to iron tricarbonyl derivatives are described herein. A unique advantage of structure‐resonance theory is that it can be applied rapidly by hand calculation, allowing numerous applications with little labor. The orbital basis for describing iron complexes allows one to use graph‐theoretical algorithms to further simplify the theoretical

ISSN:0021-2148    

DOI:10.1002/ijch.198000083

出版商:WILEY‐VCH Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractBecause of their energy additivity, acyclic conjugated hydrocarbons are used as reference structures in the computation of the aromatic character of cyclic compounds. The origin of this additivity is investigated by treating conjugated acyclics as collections of perturbed ethylene molecules. Odd order perturbations affect individual orbital energies, but, at least for most acyclics, do not change total π energies. Additivity is shown to persist through sixth order for the even terms

ISSN:0021-2148    

DOI:10.1002/ijch.198000084

出版商:WILEY‐VCH Verlag    

年代:1980

数据来源: WILEY