Kekule molecular models

Chrysene is an aromatic hydrocarbon found in coal tar. Convert the molecular model to a Lewis structure in which all of the rings correspond to Kekule formulas of benzene. 

In this same book Kekule proposes a series of ovals and spheres as molecular models. Naquet used these a few years hence. (Figure 15 (34)-) This is a full seven years before Le Bel and vanT Hoff presented their presentations as solid figures (Figure 16). In this same eventful year, Dewar, in a lecture prepared for the Royal Society of Edinburgh,... 

Baker and Rouvray 11 argued that the term Dewar benzene should be abandoned for the honour of Dewar, since he never believed that the bicyclohexadiene could be a structure of benzene. He only showed some possibilities of compounds by molecular model, which included Kekule structure and others. The authors of this article don t agree with this proposal since we should pay more attention to Dewar s proposal of a highly strained compound. Furthermore, the term Dewar benzene has become too familiar to chemists to be abandoned. Thus, we use this term in this review,... 

Baeyer s speech has considerable interest. After the expected preliminaries, he began by asking the rhetorical question Is Kekule s benzene theory a true depiction of the molecule, or is it simply a heuristically useful fiction This question evoked a consideration of molecular models. Van t Hoff was not the first to suggest a tetrahedral shape for the carbon atom, Baeyer noted it was Kekule who had introduced tetrahedral carbon models in 1867. Of course, van t Hoff had taken the idea further than Kekule, in particular by affirming that the four valence bonds emanating from each carbon atom were relatively fixed and could therefore be studied chemically. In this sense Kekule s tetrahedral models were analogous to Heinrich Hertz s famous comment about James Clerk Maxwell s equations of the electromagnetic field that they have almost an independent life, that they can appear wiser even than their creator and can yield more than was ever invested in them. ... 

Kekul s methyl chloride as a "sausage" formula, and as a molecular model. Source Kekul, Lehrbitch der organischen Chemie 0859), l 162n Museum for the History of Sciences, University of Ghent. 

Why did Baeyer not consider the possibility that cyclohexane and larger molecules are nonplanarP According to Ramsay, Baeyer used a set of Kekule tetrahedral molecular models in which half-bonds were joined with spring connectors to make bonds between atoms. This model set allowed—indeed, required—one to construct a planar representation of a cyclic molecule and then to measure angle strain by the deviation of the bonds from the straight lines between atoms. Thus, cyclohexane would be represented by the model in Figure 3.14. As is so often the case, ideas that become firmly planted in the minds of scientists are difficult to displace. Bassindale noted that by 1890, only... 

Convert each of the molecular models to a condensed structural formula, a Kekule structure, and a skeletal (line) structure. 

One can view various molecular models as predictions of molecular structure, a theoretical prediction to be more precise. Such are Kekule formulas for benzene. Doering s structure of bullvalene, that was soon synthesized by Schroder and co-work-... 

A recent summary of the history and dynamics of the theoretical models of benzene39 cites a view that even though the current molecular orbital (MO) view of benzene seems complete and ultimate while the valence bond (VB) view seems obsolete, the recent findings about zr-distortivity in benzene indicate that the benzene story is likely to take additional twists and turns that will revive the VB viewpoint (see footnote 96 in ref 39). What the present review will show is that the notion of delocalized zr-systems in Scheme 1 is an outcome of both VB and MO theories, and the chemical manifestations are reproduced at all levels. The use of VB theory leads, however, to a more natural appreciation of the zr-distortivity, while the manifestations of this ground state s zr-distortivity in the excited state of delocalized species provides for the first time a physical probe of a Kekule structure .3... 

The mathematical chemist will recognize a as one of the Kekule valence-bond structures of the hydrocarbon, while is the corres nd-ing molecular graph Model is called an inner dual or dualist [2], is a caterpillar tree [3], and is called a Clar graph [4]. The latter two models are apparently quite different from the original skeleton, however, as it will turn out later, the topological properties of this benzenoid system are best modeled by either d or e-... 

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