Kekule-Couper-Butlerov theory

The development of valency arose from Berzelius theory of chemical combination which stressed [17, 18] the electronegative and electropositive character of combining atoms. In the mid-nineteenth century, Frankland, Kekule, Couper, Butlerov and Kolbe [19-26], building on the theory of radicals, developed the theory of valency in which elements in compounds were joined by an attraction of positive and negative poles. The concept of valency preceded the discovery of the electron and the planetary view of the atom and may be traced to the 1850 paper by Frankland [19, 24]. He combined the older theories of free radicals and type theory and demonstrated that elements have the tendency to combine with other elements to form compounds containing an integer number of attached elements, e.g. in the three attached atoms M/j, NI3, four attached atoms in CH4 and five attached atoms in PCls. Based on these examples and postulates, Frankland articulated the truism ... 

When in 1958 the centennial of Kekule s and Couper s theory of chemical structure was commemorated, the Soviet Union waited three more years for their corresponding celebrations, for Soviet scholars dated the theory to a landmark paper in 1861 by one of their countrymen. The author of that paper, Aleksandr Mikhailovich Butlerov (1828-86), was a student of Nikolai Zinin and Karl Klaus at the University of Kazan, and was named professor there in 1857. During the mid-1850s he was already inclined toward the reform camp, but Butlerov s full development awaited his first trip to western Europe (from August 1857 to July... 

However, the graphs were rediscovered with other several occasions in physics by Kirchhoif s (1842) studies on electrical networks and, in chemistry, by the seminal works of Couper, Butlerov, and Kekule when founding the modem stmcture theory of chemical compounds. 

From the concept of isomerism we can trace the origins of the structural theory—the idea that a precise arrangement of atoms uniquely defines a substance Ammonium cyanate and urea are different compounds because they have different structures To some degree the structural theory was an idea whose time had come Three scientists stand out however for independently proposing the elements of the structural theory August Kekule Archibald S Couper and Alexander M Butlerov... 

Shortly thereafter but independently of Kekule Archibald S Couper a Scot working m the laboratory of Charles Adolphe Wurtz at the Ecole de Medicine m Pans and Alexan der Butlerov a Russian chemist at the University of Kazan proposed similar theories... 

Between 1858-1861, August Kekule, Archibald Scott Couper and Alexander M. Butlerov independently established one of the fundamental theories in organic chemistry The Structural Theory of Organic Compounds . 

An understanding of how elements are connected together in organic compounds can be gained from the structural theory of organic compounds. This theory is a result of the independent studies of Butlerov, Kekule" and Couper between 1857-1861. Briefly, the theory explains that ... 

Berzelius and Wohler are discussed above, and their work was foundational to the specific field of organic chemistry. After those two, three more scientists are famed for independently proposing the elements of stmctural theory. Those chemists were August Kekule, Archibald Couper and Alexander Butlerov. 

Kekule was not the only important protagonist in the rise of the set of ideas that was ultimately consolidated under the rubric "structure theory" for example, in addition to Williamson, Adolphe Wurtz, Emil Erlenmeyer, Hermann Kolbe, and Edward Frankland also played vital roles. At the time of the birth of the theory all of these men occupied respected positions in their field. Chapter 5 looks at four outsiders— Archibald Couper, Joseph Loschmidt, Aleksandr Butlerov, and Alexander Crum Brown—who at this time were relatively new to the science, but who made their marks in sometimes transformative ways during the years 1858-64. All four had definite ideas on how molecules should be conceived by the scientist and best represented for heuristic purposes. A tour of these figures provides a fuller understanding of the range of responses, opportunities, and creative options that were available during these tumultuous years in the science, and suggests par-... 

Today, a chemist makes an unconscious assumption whose validity was far from evident in the 1860s. This is that all the properties of a molecule derive solely from the atoms it contains and the way they are arranged. Although this idea may have been implicit in the work of Couper and Kekule, it was the Russian Alexander Mikhailovich Butlerov (1828-1886) who clearly and consistently advocated the structure theory. In a paper of 1861 in which he first set out his views, he said Only one rational formula is possible for each compound, and when the general laws governing the dependence of chemical properties on chemical structure have been derived, this formula will represent all these properties. . The more cautious Kekule continued to use type formulae, as well as his sausage formulae (Chapter 8), for several years after 1861. 

The issue fell on fertile ground, not so much because of the principles of dialectical materialism, but because there had been priority disputes since 1863 about the originators of the theory of chemical structure (Butlerov, Couper and Kekule), in particular between German and Russian historians. That in English publications the name of Kekule dominates, Couper may be mentioned briefly and Butlerov often not at all seems to be an obvious bias. On the other hand, it is equally wrong to claim that Butlerov is the true creator of the theory of chemical structure. Probably it is fair to say that Butlerov, Couper, and Kekule between them made all the important contributions but, because they knew each others work and met one another on their journeys, a ranking in terms of priority doesn t make much sense. It might be added that Butlerov and Kekule were personal friends, and as far as can be known did not quarrel about priority. 

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