ISSN:0570-0833    

DOI:10.1002/anie.196507291

出版商:Hüthig&Wepf Verlag    

年代:1965

数据来源: WILEY

摘要:

AbstractThe historical development of the methods to generate dehydrobenzene is outlined. Dehydrobenzene readily adds nucleophilic as well as electrophilic partners. Diels‐Alder addition to dienes is moreover a valuable synthetic principle. The intermediacy of dehydrobenzene has been proved for polar additions by labeling with14C or with a substituent. The same conclusion has been reached in Diels‐Alder additions by competition experiments. The considerable selectivity displayed by dehydrobenzene in both types of reaction is not caused by solvation, since recently the existence of dehydrobenzene in the gas phase has been established, where it reacts similarly as in solut

ISSN:0570-0833    

DOI:10.1002/anie.196507311

出版商:Hüthig&Wepf Verlag    

年代:1965

数据来源: WILEY

摘要:

AbstractThe prefix xnis proposed for the classification of valence‐bond isomers of aromatic systems, where n is the change in the number of rings or in the number of π‐bonds on isomerization. Representatives of the x1‐series are Dewar benzene and 9, 10‐dihydronaphthalene. Benzvalene and prismane belong to the x2and x3series, respectively. Various derivatives of such valence‐bond isomers have recently be

ISSN:0570-0833    

DOI:10.1002/anie.196507381

出版商:Hüthig&Wepf Verlag    

年代:1965

数据来源: WILEY

摘要:

AbstractDewar benzene, Ladenburg benzene (prismane), and a combination of these bond systems (benzvalene) have variously been discussed as planar limiting structures of benzene, although they have no physical reality. If, however, we regard these systems as non‐planar structures (as did their originators), they become chemical individuals, derivatives of which have recently been isolated. In addition to being a valance‐bond isomer of benzene, benzvalene is also the first member of a still largely hypothetical series of molecules (the valenes), in which the skeleton atoms can change places with their neighbors to produce the valencebond isomers. The best‐known representative of this class is bullv

ISSN:0570-0833    

DOI:10.1002/anie.196507461

出版商:Hüthig&Wepf Verlag    

年代:1965

数据来源: WILEY

摘要:

AbstractCompounds which undergo fast and reversible valence‐bond isomerization (i.e. which have fluctuating cyclopropyl and/or double bonds) are taken to be those in which the average life‐time of the valence‐bond isomers at 0 °C is of the order of 100 seconds at most, and for which the maximum activation energy of the bond migration is 20 kcal/mole. The fast, reversible bond shift can scarcely be detected by chemical means, but can be recognized by NMR spectroscopy, since the time for which a proton occupies a position with a given magnetic environment has a pronounced influence on the NMR spectrum. Some examples of molecules with fluctuating bonds are cyclooctatetraene and its derivatives, unsaturated seven‐ membered ring systems, homotropilidene, bridged homotropilidene systems, bullvalene, and substituted bullvalenes. The last class is particularly interesting, since here the carbon atoms are continually changing their relative positions and n

ISSN:0570-0833    

DOI:10.1002/anie.196507521

出版商:Hüthig&Wepf Verlag    

年代:1965

数据来源: WILEY

摘要:

AbstractBy “Conformational Analysis” is meant the analysis of the physical and chemical properties of a compound in terms of its preferred “conformations”, i.e. rotational arrangements about single bonds. This particular review deals with cyclohexanoid compounds capable of existing in two or more stable confor

ISSN:0570-0833    

DOI:10.1002/anie.196507611

出版商:Hüthig&Wepf Verlag    

年代:1965

数据来源: WILEY

摘要:

AbstractNuclear Magnetic Resonance is today one of the best methods available for the conformational analysis of cyclohexane derivatives. It is possible with this technique to investigate the spatial orientation of the substituents in fixed molecules, as well as the equilibrium position in mobile systems. For these determinations the areas under the signals, the chemical shifts, the coupling constants, and the band widths of particular signals can be used.

ISSN:0570-0833    

DOI:10.1002/anie.196507741

出版商:Hüthig&Wepf Verlag    

年代:1965

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196507832

出版商:Hüthig&Wepf Verlag    

年代:1965

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196507841

出版商:Hüthig&Wepf Verlag    

年代:1965

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196507853

出版商:Hüthig&Wepf Verlag    

年代:1965

数据来源: WILEY