ISSN:0021-2148    

DOI:10.1002/ijch.198200002

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractContrary to what is often believed, the description of the bonding orbitals of cyclopropane in terms of the so‐called Walsh‐orbitals or F.C.M.‐ (bent‐bond) ‐orbitals isnotequivalent. These two sets of orbitals transform into each other only if their antibonding counterparts are taken into account. The bent‐bond orbitals can be obtained directly from the set of occupied canonical SCF orbitals of cyclopropane via a unitary transformation into localized orbitals. In contrast, the bonding Walsh‐orbitals are not contained in the occupied manifold of the canonical orbitals, because of their non‐equivalence to the F.C.M.‐ orbitals. This is the reason why the anti‐bonding Walsh‐orbitals have to be taken into consideration if one wants to draw valid conclusions, e.g., about the photoelectron spectra of compounds containing th

ISSN:0021-2148    

DOI:10.1002/ijch.198200003

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThis paper examines the effect of fusing a small carbocyclic ring onto the ortho positions of an aromatic nucleus. Benzene derivatives are considered to which have been fused one, two or three small rings. The effect of varying the size and orientation of the rings is discussed with respect to changes in the σ‐ and π‐bonding networks, the geometry of these molecules and their chemical reactivity. Other aromatic nuclei, such as pyridine, thiophene, naphthalene and the tropylium ion, are also described. Variations in physical properties appear to be best explained by a rehybridization theory which functions in the plane of the system. Perturbations of the π‐bonding framework are better manifested by changes in chemical re

ISSN:0021-2148    

DOI:10.1002/ijch.198200004

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThecis‐ andtrans‐dicyano‐tris[2.2.2]‐σ‐homobenzenes9/10have been synthesized and characterized by spectroscopic methods and X‐ray structural analyses. From the relative ease of their transformations and from the products of their vapour phase pyrolyses, it is concluded that a pericyclic mechanism is no long

ISSN:0021-2148    

DOI:10.1002/ijch.198200005

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

ISSN:0021-2148    

DOI:10.1002/ijch.198200006

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe photochemistry of cyclobutanes and saturated four‐membered heterocycles with two exocyclic double bonds (except bisalkylidenecyclobutanes) is reviewed. Emphasis is laid on photoproducts rather than on mechanism, with special regard for the formation of (hetero)methylenecyclopropanes via photoextrusion of small stable molecule

ISSN:0021-2148    

DOI:10.1002/ijch.198200007

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

ISSN:0021-2148    

DOI:10.1002/ijch.198200008

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe readily available benzodihydropentalene6and dimethyl acetylene‐dicarboxylate react to give norbornadiene diester8, with a three‐carbon bridge from C1to C2. Inrradiation of8gives the corresponding C1‐C2bridged quadricyclane diester9, a new ring system. Diester9is quite stable, reverting to8with at1/2of 30 min at 170°C. The corresponding diacid11, also prepared, reverts to its norbornadiene precursor at a considerably lower temperature, possibly as a consequence of acid cat

ISSN:0021-2148    

DOI:10.1002/ijch.198200009

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractOn heating the N‐neopentylalkylideneaziridine1or4, a mixture of1, 4and N‐neopentyl‐2,2‐dimethylcyclopropanimine3is obtained. The imine3does not rearrange, but breaks down into the fragments isobutene and neopentylisocyanide. The reaction between1(or4) and methanol gives the ring‐opened products5and6and the cyclopropylamino ether7. Addition of acid gives rise to only ring‐opened products5, 6and8. It is believed that the reactions proceed via the common intermediate 2‐N‐neopentylaminoallyl cation2, followed by a rapid ring closure to the protonated isomeric aziridines1and4and 2,2‐dimethyl

ISSN:0021-2148    

DOI:10.1002/ijch.198200010

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe sign of the CD within the first absorption band (200–220 nm) of optically active vinyl‐cyclopropanes has been correlated with the absolute conformation of the chromophore in a non‐empirical way. A positive torsional angle between the C=C and the bisectrix of the cyclopropane ring between 0° and ≃ + 70° gives a positive Cotton effect; between ≃ + 110° and 180° it gives a negative one. The rule has been tested mainly on models of ter

ISSN:0021-2148    

DOI:10.1002/ijch.198200011

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY