There’s more on Kekulé and how he dreamt up the structure of benzene in Chemistry World, who also have a detailed article on Kathleen Lonsdale’s life and chemistry contributions. to pick one of the encoded Kekul e structures, to enumerate them all, etc. Comments. A. Kekulé’s Model of Benzene The first structure for benzene, proposed by August Kekulé in 1872, consisted of a six-membered ring with alternating single and double bonds and with one hydrogen bonded to each carbon. The following year he published a much longer paper in German on the same subject. The Kekulé structure, according to August Kekulé himself, came to him in a day-dream when he saw a snake seizing its own tail forming a ring structure. This was a 6 member ring of carbon atoms joined by alternate double and single bonds (as shown) This explained the C 6 H 12 molecular formula; Problems with the Kekulé Model The low reactivity of Benzene. One of the reasons for benzene’s ubiquity is its unusual ring structure rst discovered by Kekul e in 1865. The benzene example from Fig. Results •Kekulé was the first to suggest a sensible structure for benzene. The idea of the structure of benzene is one of the favourite stories in Chemistry. of the unique structure and chemical properties of benzene and its derivatives. Observe the following drawings of the structure of Retinol, the most common form of vitamin A. A detailed history of Kekule’s discovery can be found in [14, 15, 16, 18]. Introduction. Kekulé's structure of benzene stated that there were 3 double bonds and 3 single bonds. The structures of cyclohexene and cyclohexane are usually simplified in the same way that the Kekulé structure for benzene is simplified - by leaving out all the carbons and hydrogens. In this paper, we show that a simple symmetry-based analysis can narrow down possible benzene structures to three ring ones, including the Kekul e’s ring. The first drawing follows the straight-line (a.k.a. In 1865 Kekulé published a paper in French (for he was then still in Belgium) suggesting that the structure contained a six-membered ring of carbon atoms with alternating single and double bonds. •Benzene does react with bromine, but only in the presence of FeBr3 (a Lewis acid), and the reaction is a substitution, not an addition. More detail on the limitations of Kekulé’s structure, and how Lonsdale’s structure solved these, can be found on ChemGuide’s pages here and here. In the cyclohexane case, for example, there is a carbon atom at each corner, and enough hydrogens to make the total bonds on each carbon atom up to four. Kekulé's most famous work was on the structure of benzene. 1 would be encoded by c1ccccc1 in contrast to the Kekul e structure encoding C1=CC=CC=C1 discussed above. The central problem for the standard SMILES approach is the lack of a decent Benzene is one of the basic building blocks of organic molecules. •Benzene is a planar molecule (all the atoms lie in one plane), and that would also be true of the Kekulé structure. The ring system had alternating double and single bonds to allow for the C 6 H 6 structure previously accepted. According to Kekule himself, his idea of a ring was also due to an inspiration { inspired by a vision of a snake seizing its own tail [10]. The structures of cyclohexene and cyclohexane are usually simplified in the same way that the Kekulé structure for benzene is simplified – by leaving out all the carbons and hydrogens. Kekul e’s Benzene structure: usefulness of symmetry 7185 Kekule did not just use the notion of symmetry. In the cyclohexane case, for example, there is a carbon atom at each corner, and enough hydrogens to make the total bonds on each carbon atom up to four. 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