Hexagon formula

For the hexagonal composition given above, i.e.- the compound LaAlnOis. the hkl values were obtained by trying certain values in the hexagonal formula and seeing if the results give valid numbers, consistant with the numbers used. That is, a trial and error method was used to obtain the correet results. For example, one would start with 100 and determine what value of d conforms to this plane. Then, 200 and 300 would be used, etc. If we do this, we obtain the values shown in Table 2-4 as ... 

Hexagon Formula.—If in hexa-methylene the six methylene groups are symmetrically arranged we shall have a structural formula represented by a hexagon, as this geometric figure is symmetrical and of six points and six sides. This has been already shown on page 464. 

Hexagon Formula.— The hexagonal arrangement of six carbon atoms, each one of which holds in combination one hydrogen atom, gives us such a symmetrical structure for a compound whose composition is CeHe. Represented in its simplest form and as indicated by its relation to cyclo-hexane we have... 

Mono-substitution Products, alpha and beta.—In the benzene ring we found that no isomeric mono-substitution products are known and according to the hexagon formula none are possible. With naphthalene, however, two isomeric mono-suhsiituXion products are known in all classes of derivatives. Examination of the formula shows that this is possible. Positions i, 4, 5, 8 are alike and when substitution in one of these positions takes place the product is designated as an alpha compound. These four positions are different from the remaining four, viz., 2, 3, 6,... 

The way how August Kekule discovered the structural formula of benzene is one of the legends of the history of chemistry [1, 2]. In 1865/6, Kekule proposed for benzene the hexagonal formula 1 shown in Fig. 11.1, according to which the carbon atoms would be three-valent (or, in more modem terminology three-coordinate). In order to make the carbon atoms four-valent, in 1872 Kekule inserted three double bonds into his benzene formula, which can be done in two distinct ways— formulas 2 and 3 shown in Fig. 11.1. Nowadays, these are referred to as the Kekule structures or the Kekule structural formulas of benzene. 

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