Kekule sentence example

kekule
  • Organic chemistry was especially developed by the publication of Gerhardt's Traite de chimie organique in 1853-1856, and of Kekule's Lehrbuch der organischen Chemie in 1861-1882.
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  • A further generalization was effected by August Kekule, who rejected the hydrochloric acid type as unnecessary, and introduced the methane type and condensed mixed types.
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  • The ringed structure of benzene, C 6 H 61 was first suggested in 1865 by August Kekule, who represented the molecule by six CH groups placed at the six angles of a regular hexagon, the sides of which denoted the valencies saturated by adjacent carbon atoms, the fourth valencies of each carbon atom being represented as saturated along alternate sides.
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  • This formula, notwithstanding many attempts at both disproving and modifying it, has well stood the test of time; the subject has been the basis of constant discussion, many variations have been proposed, but the original conception of Kekule remains quite as convenient as any of the newer forms, especially when considering the syntheses and decompositions of the benzene complex.
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  • Although Kekule founded his famous benzene formula in 1865 on the assumptions that the six hydrogen atoms in benzene are equivalent and that the molecule is symmetrical, i.e.
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  • If we accept Kekule's formula for the benzene nucleus, then we may expect the double linkages to be opened up partially, either by oxidation or reduction, with the formation of di-, tetra-, or hexa-hydro derivatives, or entirely, with the production of open chain compounds.
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  • More important are Kekule's observations that nitrous acid oxidizes pyrocatechol or [I.2]-dioxybenzene, and protocatechuic acid or [3.4]- dioxybenzoic acid to dioxytartaric acid, (C(OH) 2 COOH) 2 (Ann., 1883, 221, p. 230); and 0.
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  • Carius showed that potassium chlorate and sulphuric acid oxidized benzene to trichlorphenomalic acid, a substance afterwards investigated by Kekule and 0.
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  • The value of this ringed structure was readily perceived, but objections were raised with respect to Kekule's disposal of the fourth valencies.
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  • This view was opposed by Victor Meyer and Kekule.
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  • Kekule answered Ladenburg by formulating a dynamic interpretation of valency.
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  • Knoevenagel's theory of " motoisomerism," have been brought forward to cause these facts to support Kekule.
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  • Therefore, according to Kekule, the double linkages are in a state of continual oscillation, and if his dynamical notion of valency, or a similar hypothesis, be correct, then the difference between the 1.2 and 1.6 di-derivatives rests on the insufficiency of his formula, which represents the configuration during one set of oscillations only.
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  • This implied that in the benzene complex there was at least one carbon atom linked to three others, thus rendering Kekule's formula impossible and Ladenburg's and Claus' possible.
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  • Kekule (Ann., 1883, 221, p. 230), however, reinvestigated this acid; he showed that it was dibasic and not tribasic; that it gave tartaric acid on reduction; and, finally, that it was dioxytartaric acid, HOOC C(OH) 2 C(OH) 2 COOH.
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  • The formation of this substance readily follows from Kekule's formula, while considerable difficulties are met with when one attempts an explanation based on Ladenburg's representation.
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  • By projecting Ladenburg's prism on a plane and numbering the atoms so as to correspond with Kekule's form, viz.
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  • The stronger argument against the ethylenoid linkages demanded by Kekule's formula is provided by the remarkable stability towards oxidizing and reducing agents which characterizes all benzenoid compounds.
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  • A similar contradiction apparently exists with regard to the specific volume, for while benzene has a specific volume correspinding to Claus' formula, toluene, or methylbenzene, rather points to Kekule's.
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  • Stohmann of Leipzig; and the new data and the conclusions to be drawn from them formed the subject of much discussion, Briihl endeavouring to show how they supported Kekule's formula, while Thomsen maintained that they demanded the benzene union to have a different heat of combustion from the acetylene union.
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  • It was found that the results were capable of expression by the empirical relation CaH2b= 104.3b+49'09m+105.47n, where C a H 2b denotes the formula of the hydrocarbon, m the number of single carbon linkings and n the number of double linkings, m and n being calculated on the Kekule formulae.
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  • Two acids corresponding to the formula of Kekule and Claus are triphenyl acrylic acid, (C6H5)2C: C([[Cooh) C 6 H]],, and triphenyl acetic acid, (C,H,),C 000H.
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  • Experiments showed that the second acid was much more difficult to esterify than the first, pointing to the conclusion that Claus' formula for benzene was more probable than Kekule's.
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  • Formula (4) is symmetrical and based on Kekule's formula: it is in full accord with the syntheses and decompositions of the naphthalene nucleus and the number of isomers found.
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  • The former, based on Kekule's symbol for benzene, explains the decompositions and syntheses of the ring, but the character of naphthalene is not in keeping with the presence of five double linkages, although it is more readily acted upon than benzene is.
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  • Kekule at Ghent, then visited England, studied in Paris and with Ch.
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  • He was educated at Dollar Academy and Edinburgh University, being at the latter first a pupil, and afterwards the assistant, of Lord Playfair, then professor of chemistry; he also studied under Kekule at Ghent.
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  • Kekule's main importance lies in the far-reaching contributions which he made to chemical theory, especially in regard to the constitution of the carbon compounds.
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  • Frankland, when in 1858 Kekule published a paper in which, after giving reasons for regarding carbon as a tetravalent element, he set forth the essential features of his famous doctrine of the linking of atoms. He explained that in substances containing several carbon atoms it must be assumed that some of the affinities of each carbon atom are bound by the affinities of the atoms of other elements contained in the substance, and some by an equal number of the affinities of the other carbon atoms. The simplest case is when two carbon atoms are combined so that one affinity of the one is tied to one affinity of the other; two, therefore, of the affinities of the two atoms are occupied in keeping the two atoms together, and only the remaining six are available for atoms of other elements.
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  • This conception led Kekule to his "closed-chain" or "ring" theory of the constitution of benzene which has been called the "most brilliant piece of prediction to be found in the whole range of organic chemistry," and this in turn led in particular to the elucidation of the constitution of the "aromatic compounds," and in general to new methods of chemical synthesis and decomposition, and to a deeper insight into the composition of numberless organic bodies and their mutual relations.
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  • Japp, in the Kekule memorial lecture he delivered before the London Chemical Society on the 15th of December 1897, declared that three-fourths of modern organic chemistry is directly or indirectly the product of Kekule's benzene theory, and that without its guidance and inspiration the industries of the coal-tar colours and artificial therapeutic agents in their present form and extension would have been inconceivable.
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  • Many of Kekule's papers appeared in the Annalen der Chemie, of which he was editor, and he also published an important work, Lehrbuch der organischen Chemie, of which the first three volumes are dated 1861, 1866 and 1882, while of the fourth only one small section was issued in 1887.
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  • Kekule, and in 1858 took his degree as Ph.D.
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  • The formulae of Kekule, Divers and Armstrong have been discarded, and it remains to be shown whether Nef's carbonyloxime formula (or the bimolecular formula of Steiner) or Scholl's glyoxime peroxide formula is correct.
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  • Kekule was the forerunner of his celebrated benzene theory in particular, and of the universal application of structural formulae to the representation of the most complex organic compounds equally lucidly as the representation of the simplest salts.
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  • The pioneer in this field was August Kekule, who, in 1865 (Ann., 137, p. 129; see also his Lehrbuch der organischen Chemie), submitted his well-known formula for benzene, so founding the " benzene theory " and opening up a problem which, notwithstanding the immense amount of labour since bestowed upon it, still remains imperfectly solved.
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  • He admitted the possibility of the formulae of Kekule, Claus, Dewar and Ladenburg, although as to the last di-trimethylene derivatives should be possible reduction products, being formed by severing two of the prism edges; and he attempted to solve the problem by a systematic investigation of the reduced phthalic acids.
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  • The relative merits of the formulae of Kekule, Claus and Dewar were next investigated by means of the reduction products of benzene, it being Baeyer's intention to detect whether double linkages were or were not present in the benzene complex.
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  • But the formation of the A2.5 acid as the first reduction product is not fully consistent with Kekule's symbol, for we should then expect the or the acid to be first formed (see also Polymethylenes).
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  • (The stereo-chemistry of carbon compounds has led to the spatial representation of a carbon atom as being situated at the centre of a tetrahedron, the four valencies being directed towards the apices; see above, and Isomerism.) A form based on Kekule's formula consists in taking three pairs of tetrahedra, each pair having a side in common, and joining them up along the sides of a regular hexagon by means of their apices.
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  • One of the most important applications of these values is found in the case of the constitution of benzene, where Thomsen decides in favour of the Claus formula, involving nine single carbon linkages, and rejects the Kekule formula, which has three single and three double bonds (see section IV.).
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  • Virchow's conjecture as to the starchy nature of the substance was disproved by Friedrich and Kekule, who confirmed Professor Miller's previous finding as to its albuminous or protein nature.
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